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<text> This program was designed to train office staff, educate patients, and to supplement Optometry student's class notes. The data was compiled from Optometry professors, students of Optometry and the public domain. The program is very easy to use, simply click the mouse on the desired topic and "Ocular Anatomy Tutor" will take you there. There is a list of "KEY" words which will also do the same. The buttons to the left will take you back to the finder, to the HyperCard "Home" card, and allow you to continue with "Ocular Anatomy Tutor". The arrow in the upper left corner of the topics page will return you to here. While in the Data areas, the arrow buttons at the bottom of the page will move you to the next or previous sections, respectively. The "eye" button will return you to the Topic page. The diagram numbers can be clicked for further reference. To get rid of the diagram just click on the "return" button. A manual of the entire outline is available from the author for a small fee of $15.00 plus $1.50 shipping and handling. Please send check or money order to: Dr. Mark C. Wade 611 Menlo Park Road Green Bay, WI 54302 (414) 468 - 0403 Questions or comments are appreciated. If this type of program is utilized and liked by the user please let me know, a pathology and pharmacology program are also planned. You can register your copy of this program and obtain future updates by sending $5.00 to the author, if you purchase the entire manual above it also entitles you to future updates and other information as it comes available. Another program, called "Coffey Cake" is a visual therapy analysis program which diagnoses, generates insurance codes, and lays out a plan for training techniques. There is also a supplemental manual of over one hundred pages full of VT training techniques to utilize in your practice. Dr. Wade can answer any questions about these advanced programs. All of the programs are designed to increase the value of any practice while maintaining a high tech professional image with your patients.</text>
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<text>10 Retinal LayersAbbreviationsAdie's Tonic PupilAgainst the Rule AstigmatismAmacrineAmpullaAngoid StreaksAnnulus of ZinnAphakiaAqueous Removal PathwayArachnoidArgyll Robertson PupilAxial LengthBipolarBlood Supply to the BrainBowman's LayerBranches of the Ophthalmic ArteryBreakup TimeBruch's MembraneBrucke's MuscleCataractsChoriocapillarisChoroidCircle of WillisCloquet's CanalColobomaCorneal MetabolismCrypts of FuchsCrystalline LensDescemet's LayerDilator MuscleDrusenDuctionDuraEctodermEfferent Nervous SystemEmbryologyEnd ArteriesEndodermEndotheliumEpimysiumExternal Limiting MembraneEyelidsFacial NerveFiber Baskets of SchultzeField ChangesGanglion CellGlaucomaGoblet CellsGonioscopyGross AnatomyHaller's LayerHassal Henle WartsHemi-DesmosomeHenle's Fiber LayerHorner's MuscleHorner's SyndromeHyalocytesInferior ObliqueInferior RectusInnervation of the EyeIOPIschemiaKnees of WilbrandKrauseLamina CribrosaLateral Geniculate NucleusLateral RectusLGNLigament of WeigerLimbusLoops of MeyerLymphatic Circle of TeichmannMacula AdherensMajor Circle of the IrisMarcus GunnMedial RectusMeibomian GlandMelanomaMesodermMinor Circle of the IrisMittendorf DotMollMuller's MuscleMuscle of RiolanMydriasisNerve Fiber LayerOblique AstigmatismOptic NerveOuter Nuclear LayerOuter Plexiform LayerPars PlanaPars PlicataPatellar FossaPeriorbital Connective TissuePhotopicPhotoreceptorPiaPores of FontanaRAPDRetinal Pigmented EpitheliumRod/Cone LayerRouget CellsSattler's LayerSchlemm's CanalSchwalbe's LineScotopicSleep ReflexSomatic SystemSpace of BergerSpace of MartegianiStellateStriae of GennariStromaStructure of the EyeSuperior ObliqueSuperior RectusSuspensory Ligament of LockwoodTenon's CapsuleTerms and FactsTrabecular MeshworkTrigeminalUveal TractValleys of KuhntValve of HasnerVersionvon HerrickWith the Rule AstigmatismWolfringZeisZonula OccludensZonule of Zinn</text>
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<text>Gross Anatomy of the EyeThe eye is commonly referred to as "Oculus Bulbi". See diagram 1.Dimensions: A. Shape: The eye is made of two partial spheres. 1. Anterior radius = 8 millimeters, 1.6 of total area, (cornea). 2. Posterior radius = 12 mm., 5/6 of the total area, (sclera). B. Size: Varies with age, sex, race, physiology. 1. Average adult eye: a. Diameter is 24 mm. b. Superior to inferior is 23 mm. c. Nasal to temporal is 23.5 mm. d. Anterior to posterior is 24 mm. (Axial length)(the distance from apex of cornea to the fovea) 1. Emmetrope has an axial length of 24 mm. 2. Myope (near-sighted) has an axial length > 24 mm. 3. Hyperope (far-sighted) has an axial length < 24 mm. 4. Presbyope is a reduced accommodative ability normally occurring with age. 2. Development: a. Axial length at birth measures 16-17 mm. b. Axial length at 3 years measures 22.5-23 mm. c. By age 13 the axial length is adult size. (24 mm.) STRUCTURE of the EYE: (See diagram 2) A. Fibrous tunic: The outermost layer, which maintains the size and shape of the eye. 1. Collagenous: Outermost layer 2. Posterior: Sclera which is white and opaque. 3. Anterior: Cornea which is clear. 4. Limbus: The junction of the cornea and sclera. 5. External scleral sulcus: The depression at the limbus. B. Uveal Tract: The middle layer, which provides nutrition to the eye. 1. Anterior uvea: a. Iris: Main function is light diaphragm. b. Ciliary body: Main functions are making aqueous and vitreous, and accommodation. 2. Posterior uvea: a. Choroid: Main function is suppling nutrition to the retina. 3. The anterior and posterior uvea meet at the ora serrata. C. Retina: 1. The retina is an extension of the central nervous system. 2. It extends from the optic nerve to the ora serrata. 3. The retina translates light energy to neural action potential. 4. The optic nerve transfers information to the brain. D. Chambers of the eye: 1. Anterior chamber: (area between iris and the vitreous) a. Bounded by the cornea, ciliary body, sclera, iris, and pupil. b. The maximum depth is 2.5 mm. c. It contains .25 milliliters of aqueous. 2. Posterior Chamber: a. Bounded by iris, ciliary body, vitreous, lens, and the pupil. b. It contains .06 milliliters of aqueous. 3. Vitreous: (area behind the lens) a. Bounded by the ciliary body, retina, lens and posterior chamber. b. It consists of a transparent gelatinous material, which contributes to the shape of the eye.</text>
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<text>CORNEA:I. Dimensions: Partial sphere or ellipsoid. A. Radius = 7.8 mm. (flatter at periphery, more curved at apex) B. Horizontal = 12 mm. Vertical = 11 mm. 1. Megalocornea is a vertical measurement of > 12 mm. 2. Microcornea is a vertical measurement of < 10 mm. 3. Astigmatism is when the different meridians have a different refractive power, a shorter radius means a steeper curvature. a. With the rule astigmatism: Greater refraction in the vertical, (axis 90). b. No astigmatism: vertical refraction = horizontal. c. Against the rule astigmatism: Greater refraction in the horizontal, (axis 180). d. Oblique astigmatism: Greatest refraction in a meridian other than the vertical or horizontal. C. Thickness: .52 - .57 mm. 1. Edema: Thicker due to water absorption. 2. Keratoconus: Thinner due to uneven endothelial cells.II. Functions of the cornea: A. Refracts light: About 43 diopters, lens refracts about 15 - 20 diopters, totaling about 60 diopters for whole eye. B. Transmits light: 1. Factors in transparency: a. Regular arrangement of stromal collagen fibers. If disturbed a scar or opacity is formed. b. The degree of hydration is 75% - 80% water. c. No blood vessels are present. d. Regularity and smoothness of epithelium.III. Types of intercellular junctions: A. Zonula Occludens (ZO): Occluded intercellular space, cell membranes are touching, tight junctions, water and small molecules must move through cells, cannot move between. B. Zonula Adherens (ZA): Cellular space and cell membranes maintained. C. Macula Adherens, Desmosomal type (MA-DESM): Look like spot welds, intercellular cement, tonofilaments from each side attached to electron dense plate between cell membranes. D. Macula Adherens (MA): Fine fibrils, button-like, intercellular space maintained. E. Macula Occludens (MO): Adjacent cell membranes fused, tight junctions F. Hemi-Desmosome (HEMI-DESM): Fibrils attach to basement membrane, one sided. G. Basement membrane: Filaments continue into underlying connective tissue, has electron dense layer of attachment of fibrils from HEMI-DESM.IV. Histology of the Cornea (6 layers): A. Corneal epithelium: 1. Continuous at limbus with conjunctival epithelium. 2. Must be smooth and aligned for best vision. 3. Stratified squamous 5-6 cells thick. a. Basal: Most posterior, single layer, columnar, constant miosis, push off surface cells, connected to basement membrane by HEMI-DESM junctions. b. Wing cells: 2-3 layers, polyhedral. c. Surface cells: 1-2 layers, unkeratinized squamous, constantly slough off into tears, joined by ZO junctions. 1. They contain microvillae and microplicae (fingers projecting out into tears), covered with mucus which acts as a wetting agent. 4. Regeneration of corneal epithelium: a. Takes 24-48 hours. b. Utilizes migration and mitosis. B. Basement membrane: Very thin. 1. Is secreted by basal epithelial cells. 2. Has fine fibrils in muco-protein matrix. 3. Repair of damage takes 2-3 months and may not align properly. 4. HEMI-DESM from epithelium go through basement membrane into Bowman's. 5. Poor attachment of HEMI-DESM results in corneal erosion. C. Bowman's layer: 1. Acellular modified stroma, gradual transition into stroma. 2. Irregularly dispersed collagen fibers. 3. Acellular, therefore, it will not regenerate, damaged will be filled in with stroma or epithelium. D. Stroma (Substansia propria): 1. Constitutes 90% of corneal thickness. 2. 200+ lamellae parallel to the surface. a. Each lamellae is a band of uniformly straight collagen fibers. b. Adjacent lamellae are at angles to each other. c. The lamellae run from limbus to limbus. d. Each fiber has an MPS sheath. 1) MPS: chondroitin, chondroitin sulfate, keratin sulfate. 2) MPS controls arrangement of fibers. 3) MPS controls hydration, acts as an an-ion (-), which combines water and cat-ions (+). 3. Cells of the stroma: a. Fibroblast (keratocyte): 1) Produces collagen. 2) Have many processes which are sandwiched between lamellae. b. Wandering WBC: Are between lamellae. 4. Repair of damage: a. Fibroblasts will divide if collagen demand becomes great. b. Fibroblasts will also produce new collagen, usually irregular and forms a scar or opacity. E. Descemet's layer: 1. Acellular. 2. Secreted by the endothelial cells. 3. Acts as a basement membrane for endothelium, it is not bonded well at either side and separates easily. 4. Collagen fiber layers are parallel to the surface. 5. Schwalbe's line: Collagen ring at limbus, keeps Descemet's from curling up. 6. Thickens with age. a. At birth it is the same thickness as endothelium. b. Adult thickness is 2-3 times the endothelium. 7. It can be regenerated if damaged. 8. Hassal Henle warts: Areas of Descemet's that has thickened, in the periphery. F. Endothelium: 1. A single layer of hexagonal squamous cells. 2. Microvillae project into anterior chamber. 3. ZO junctions: a. Not perfect, but keep water out. b. Cells contain metabolic pumps that remove water and waste. 4. Absorbs metabolants for aqueous. 5. If damaged the adjacent cells spread out to cover, but this leaves a thin are which is more susceptible to further damage. (See diagram 1) V. Corneal metabolism: A. Oxygen: 1. 90% of the corneal oxygen is used in the epithelium, which makes sense, because 90% of all corneal cells are found here. 2. Oxygen source for the epithelium is the tears. 3. Oxygen source for the endothelium is the aqueous. B. Glucose: Obtained from the aqueous, diffuses through the stroma to the epithelium. C. Metabolic pathways: 1. Anaerobic glycolysis: Lactic acid. 2. Kreb's cycle: Preferred route. 3. Hexose monophosphate shunt: Produces 5C sugars for DNA/RNA. VI. Corneal innervation: A. Fifth (V) cranial nerve (Trigeminal): Sensory for face and eyes. B. Nerve path: Trigeminal-long ciliary nerves-they enter stroma at limbus, where myelin sheath is lost- they branch and turn 90 degrees through Bowman's- they lose their Schwann cell sheath and end in posterior 3 layers of epithelium (basal and wing cell layers). </text>
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<text>Sclera:I. Description: Posterior 5/6 of the eye. A. Color: Normally white. 1. Yellow: Due to aging, fat, or jaundice. 2. Blue: Present in infants or pathology (thinned sclera). B. Thickness: 1. Thickest anterior to extraocular muscles and at posterior pole. 2. Thinnest posterior to extraocular muscles. 3. Lamina cribrosa: Net of scleral fibers, allows optic nerve passage, this is the weakest part of the sclera, in high intraocular pressure the optic disk will become cupped. C. Structure: 1. Bundles of collagen fiber, mostly parallel to the surface, all oriented in different directions and interweaved. 2. Fibroblasts 3. No MPS: OpaqueII. Layers of the Sclera: A. Episclera: Loose connective tissue, outer layer. 1. Merges with sclera on inside and Tenon's capsule on outside. B. Sclera: No sharp division between sclera and choroid. C. Lamina fusca: Transition between sclera and choroid, melanocytes are present.III. Blood supply: A. Sclera: Avascular. B. Episclera: Rich in blood vessels, purple in color. C. Conjunctiva: Thin covering over anterior sclera, contains blood vessels and is red in color.IV. Innervation: A. Not highly innervated. B. Ciliary nerves pass through the sclera to anterior surface.V. Function of the Sclera: A. Maintains the shape of the eye. B. Provides an attachment for the extraocular muscles. C. Counters intraocular pressure.Limbus:I. Location: A. Located at the junction of the cornea and sclera.II. Occurrences at the limbus: A. Corneal epithelium (5-6 layers) changes to conjunctival epithelium (10-15 layers). B. Corneal stroma which is regular collagen becomes sclera which is irregular. C. Blood vessels: 1. Conjunctival capillaries end in limbal loops (red). 2. Episcleral capillaries end in loops, at a place further away from the limbus, these are deeper and appear purple. 3. Lymphatics collect into lymphatic circle of Teichmann. 4. Nerves: Ciliary nerves branch to limbus and cornea.III. Function of the limbus: A. Nourishment of peripheral cornea. B. Removal of aqueous. C. Attachment of ciliary muscles at the scleral spur of dense collagen fibers.IV. Removal of aqueous: A. Structures: 1. Trabecular meshwork: a. Triangular cross section, apex is at Schwalbe's line, inner along anterior chamber, base along ciliary body and scleral spur, outer along Schlemm's canal and stromal tissue. b. Occupies most of internal scleral sulcus. c. 15 flat perforated sheets (mostly holes) running from Schwalbe's line to the scleral spur (pores of Fontana). Spaces between the sheets are called the spaces of Fontana. d. The sheets are random collagen fibers with basement membranes and one layer of endothelial cells on each side. 2. Schlemm's canal (sinus venosus scleral): a. It is considered a vein, although it does not carry blood. b. It is circular around the limbus. c. It has a thick connective tissue wall and an endothelial lining. d. Has giant vacuoles on inner wall, lets in more aqueous. e. The internal collector channels of Schlemm's canal intersperse with the trabecular meshwork, but do not join. B. Aqueous removal pathway: (See diagram 1) C. Glaucoma: Increased intraocular pressure (IOP) could result from reduced aqueous outflow. 1. Open angle glaucoma: 95%, anatomical cause unknown. 2. Angle closure glaucoma: 5%, iris root obstructs trabecular meshwork. a. Assessment by von Herrick or gonioscopy. In gonioscopy you should see: 1) Scleral spur 2) Trabecular meshwork 3) Schlemm's canal 4) Schwalbe's line. b. Normal IOP is about 15 mm. of Hg., it can shoot up to 70 mm. Hg very rapidly. 3. Treatment of glaucoma: Pilocarpine, which makes ciliary muscles contract, thus opening the trabecular meshwork. 4. Ocular hypertension: Higher than normal IOP, not considered glaucoma until eye damage (usually fields) is encountered.</text>
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<text>Uveal Tract: I. Iris: A. Description: 1. Diaphram controlling the light to the retina. 2. Extends from ciliary body to pupillary margin. 3. Lens pushes forward into cone shape. 4. Separates aqueous into anterior and posterior chambers. 5. Iris root is the area of attachment at ciliary body and is thin and easily damaged. B. Pupillary changes: 1. Miosis: Smaller/constriction. 2. Mydriasis: Larger/dilation. C. Synechiae: Usually temporary: 1. Posterior: Adhesion of posterior iris to lens. 2. Anterior: Adhesion of anterior iris to cornea. D. Histology of the iris: 1. Anterior border layer: Anterior limiting membrane (cells are not connected). a. Modification of stroma. b. Relatively low in collagen. c. Layers: 1. Anterior single layer of fibroblasts. 2. Layer of melanocytes. d. Color of eye depends on number of melanocytes. 2. Stroma: a. Loose arrangement of collagen fibers. b. MPS ground substance. c. Collagen arranged in radial columns, iris trabeculae, and associated with blood vessels. d. Blood vessels: Radial, vary with pupil opening. e. Anastomoses: Joining of blood vessels. 1. Major circle of the iris: (circulus vasculosis iridis major), located in the ciliary body and supplies the iris. 2. Minor circle of the iris: (circulus vasculosis iridus minor), incomplete circle, 2/3 of iris outside, 1/3 inside. 3. Radial blood vessels: Thick collagenous adventitia, most other BV's don't have much collagen. f. Innervation: 1. Sensory, feeds into cranial(V), trigeminal. 2. Sympathetic and parasympathetic. 3. No somatic nerves. g. Iris sphincter muscle: (sphincter pupillae) 1. Surrounds pupil at pupillary margin. 2. Smooth muscle. 3. Contraction causes miosis. 4. Firmly attached to stroma, and will function even if cut in iridectomy. 5. Parasympathetic innervation via short ciliary nerves. h. Cells of the stroma: 1. Melanocytes: Not as many ay anterior border layer. 2. Clump cells: Round, contain melanin granules, occur most often near sphincter, may be either: a. Macrophages with ingested melanin. b. Misplaced neural ectodermal cells. 3. Fibroblasts. 4. Wandering leucocytes (WBC). 3. Anterior epithelium: (dilator muscle) This lies in the middle of the iris, even though it's called anterior. (See diagram 1) a. One layer thick, but basal processes overlap (3-5 layers). b. Contraction opens pupil: mydriasis. c. The origin of the dilator is in the iris root. d. Dilator muscle ends at mid-point of sphincter, but apical portion continues to pupillary margin as an epithelial cell layer. e. Innervation is sympathetic via long ciliary nerves. 4. Posterior epithelium: a. Single layer of pigmented columnar. b. Breaking of posterior synechiae may leave black clump of cells on lens surface. E. Visible structures of the iris: 1. Collaret: 1.6 mm. from pupillary margin. a. Crypts of Fuchs: Depressions with no anterior border layer covering, correspondes to area of minor circle of iris. b. Pupillary membrane of the fetus attaches at collaret. 2. Pupillary zone: From collaret to pupil. 3. Ciliary zone: From collaret to iris root. 4. Pupillary ruff or fringe: Iris epithelium rolled over pupillary margin. 5. Peripheral crypts: Crypts near iris root. 6. Sphincter muscle: Visible in infants with light blue eyes. 7. Contraction furrows: Circular folds in the ciliary zone when pupil dilates. 8. Iris process: Anterior process of the iris bridge the angle to trabecular meshwork, very narrow. F. Posterior structures of the iris: 1. Very dark pigmentation, 2 layers thick. 2. Radial contraction folds of Schwalbe in pupillary region. 3. Structural folds (furrows) of Schwalbe, radial, in ciliary region which are continuous with valleys of Kuhnt. 4. Circular folds: Near iris root, result from thickness variation in posterior epithelium.II. Ciliary body: A. Location: 1. Anterior border: Scleral spur, major circle, iris root, and anterior chamber. 2. Posterior border: Ora serrata. B. Components: 1. Pars plana (obicularis ciliaris): Posterior portion from ora serrata to ciliary processes. 2. Pars plicata (corona ciliaris): From pars plana to iris root. a. 60-70 processes. b. Between processes are the valleys of Kuhnt. C. Functions: 1. Produces aqueous: Epithelium of pars plicata, secreted into canal of Hannover. 2. Produces hyaluronic acid (MPS) for vitreous in pars plana. 3. Controls accommodation: Muscles contract relaxing zonule fibers, anterior surface of lens bulges and thus increasing refraction for near vision. D. Six (6) layers of the ciliary body: 1. Supraciliaris (supra ciliary lamina): a. Loose connective tissue connecting ciliary body to sclera, allows motion between ciliary body and sclera, very thin, this is where a detachment will happen. 2. Muscle layer: 3 sets that work as one. a. Longitudinal or meridional fibers: Outer most, Brucke's muscle. 1. Anterior origin is in scleral spur and trabecular meshwork. 2. Insertion ends in branched stellate (star-like) forms in supraciliaris posterior to ora serrata or in muscle layer anterior to ora serrata. (they run into the choroid). b. Oblique muscle fibers: Middle layer, radial, scleral spur to posterior ciliary processes. c. Muller's muscle: Inner layer, circular band of fibers, main sphincter at base of ciliary processes. 1. Connective tissue fibers attach it to scleral spur. 2. Lies near major circle. 3. Small in children, but develops from accommodation, absent in newborns. 3. Stroma: a. Highly vascularized, contains the major circle of the iris. b. Connective tissue, there is no choriocapillaris. c. Each process has a core of stroma with many capillaries. d. Capillaries in stroma are fenestrated to allow flow of large quantities of water and metabolites to epithelium for aqueous production. 4. Basal lamina (external basal membrane): a. Secreted by outer layer of epithelial cells. b. Continuous with Bruch's membrane of the choroid. 5. Epithelium: 2 single layers. a. Outer: heavily pigmented, continuous with pigmented epithelium of retina, and with anterior epithelium of the iris. b. Inner: Non-pigmented, continuous with neural layer of retina (unpigmented) and posterior epithelium of iris (pigmented). c. Both layers show reciprocal infoldings, between cells of inner layer are ZO junctions, cells connect laterally. (See diagram 2) 6. Internal limiting membrane: a. Basement membrane secreted by non-pigmented inner epithelium. b. Adjacent to aqueous. c. Continuous with internal limiting membrane of retina. d. Attachment for vitreous in pars plana. e. Attachment for zonule fibers in valley of Kuhnt. (See diagram 3) E. Aqueous production: 3 ways aqueous is made. 1. Both epithelial layers: a. Secretion, filtration, diffusion. b. Pathway is as follows: (See diagram 4) c. Posterior or anterior synechiae can restrict flow.III. Choroid: A. Location: Between sclera and retina, running from optic disc to ora serrata. B. Functions: 1. Suppress internal scattering of light, the pigment absorbs light. 2. Nourishes outer half of retina. 3. Nourishes optic disc. 4. Nourishes entire fovea (only supply to fovea). C. Layers of the choroid: Outer to inner. 1. Lamina fusca (suprachoroid lamina): a. Loose mesh of diagonal collagen fibers attaching to sclera. b. Not distinct from sclera or choroid. c. Numerous melanocytes. d. Allows "give" as choroidal blood vessels dilate and constrict. e. Long posterior ciliary arteries and long ciliary nerves pass through the lamina fusca ( sympathetic, parasympathetic, and sensory). f. Muscle stars from longitudinal ciliary muscle are found in periphery. 2. Stroma: a. Loose connective tissue. b. Contains many blood vessels, the layers themselves describe the vessel size (these are short ciliary vessels). 1. Haller's layer: Outer, next to sclera, large vessels. 2. Sattler's layer: Inner, medium vessels. c. The blood vessels are valveless. d. Innervation of blood vessels: Sympathetic via short posterior ciliary nerves. e. Contains fewer melanocytes than the lamina fusca. f. Fibroblasts. g. Wandering WBC's. f. Mast cells which release histamine. 3. Choriocapillaris: a. Meshwork of anastomosing capillaries. b. 3-4 times wider than normal capillaries. c. Cellwall: Single layer, fenestrated, perforations are covered by membrane. d. Pericytes (Rouget cells): These cells are wrapped around the capillaries and help move the blood inside them. e. The capillary nest is densest at the macula, mainly because this is the only blood supply to the fovea. 4. Bruch's membrane: Basal lamina of the choroid, has 5 layers which are listed from inner to outer: 1. Basement membrane of the retinal pigmented epithelium (RPE). 2. Inner collagenous zone. 3. Elastic zone: True elastic fibers which hold retina in place. 4. Outer collagenous zone. 5. Basement membrane of endothelial cells of choriocapillaris. a. Serves as elastic sheet holding choroid to sclera, if cut the edges pull back forming a choroidal hematoma. b. Angoid streaks: breaks in the membrane, streaks usually radiate from the optic disc. c. Drusen: Small yellow dots on the fundus, nodule of basement in inner collagenous zone, this displaces the RPE inward, near the macula in elderly people. D. Blood supply to the choroid: 1. Major supply is as follows: (See diagram 5) 2. Peripheral choroidal supply is as follows: (See diagram 6) 3. Both major supply and peripheral supply leave via the vortex veins. (See diagram 7)IV. Summary of the Uveal tract: Iris, ciliary body, and choroid. A. Firmly attached to sclera at scleral spur and optic disc. B. Loosely attached to sclera elsewhere via supraciliaris and lamina fusca. C. Flow of blood: 1. Sympathetic: constricts. 2. Parasympathetic: dilates. 3. Partially controlled by pericytes. D. High concentration of blood vessels: Inflammations are common (iritis, cyclitis, choroiditis). E. Most common malignancy is a melanoma. F. Choroid necessary for good vision: Nutrition of the retina and fovea. G. Controls the IOP by aqueous production in the ciliary body. H. Accommodation and pupillary control which is required for good vision. I. Albino retina has choroidal vessels showing.</text>
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<text>IV. Zonule of Zinn: Suspensory ligaments of the lens. A. Description: 1. Thin suspension fibers. 2. Collagen like glucoprotein and MPS (probably chondroitin sulfate) 3. Approximately 140 bundles: One on each side of every ciliary process. Each bundle contains some of all six types of fibers. B. Categories of fibers: 1. Orbiculo-Posterior: From pars plana (orbicularis ciliaris) to posterior lens capsule at ligament of Weiger. 2. Orbiculo-Anterior: Thickest and strongest fibers. From pars plana to anterior lens capsule through valley of Kuhnt. These are used for accommodation. 3. Orbiculo-Ciliary: Prevent forward movement of processes. From pars plana to base of ciliary processes. (These are auxiliary fibers). 4. Cilio-Posterior: Most abundant fibers. Prevent backward movement of lens. From valleys of Kuhnt to ligament of Weiger. 5. Cilio-Equatorial: From the valley of Kuhnt to the equator. 6. Interciliary: Between ciliary processes, holding them apart. (These are auxiliary fibers).V. Crystalline lens: A. Description: 1. Flattened globe, biconvex. 2. Features: (See diagram1) 3. Demensions: a. Equatorial diameter = 10 mm. b. Thickness: 4 mm. in a presbyope, it thickens with accommodation. B. Histology: 1. Lens capsule: Thin at the poles and equator. a. Secreted as a basement membrane by the epithelium in embryonic development. b. Composed of collagen like glucoprotein. c. Attachments for zonule fibers are on the capsule. 2. Anterior epithelium: a. Does not cover posterior surface. b. Single layer of cuboidal cells. c. Metabolically active, getting its metabolites from the aqueous. d. Cells undergo constant mitosis in posterior pre-equatorial zone. 1. One daughter cell stays in epithelium. 2. Other daughter cell elongates toward poles and becomes a cell fiber. 3. Lens fibers: a. Each fiber is a single cell from pole to pole across equator. b. Fibers meet at sutures, at poles. c. Fibers pressed inward, they lose nuclei with age.d. Nuclei of fibers form bow in equatorial area. e. Each fiber is hexagonal in cross section. f. Cell membranes are interdigitated with all adjacent cells, there is very little intercellular space, this allows for plasticity for accommodation. g. Zones of discontinuity: 1. Embryonic nucleus: Spherical, develops in utero at 2-8 weeks, is formed by primary lens fibers, this is the oldest and densest layer, they have the highest index of refraction. 2. Fetal nucleus: Forms from 3 months to birth, these are the secondary lens fibers which develop from the anterior epithelial cells, Y-sutures are formed by them (Y-anterior surface, inverted Y on posterior surface). 3. Adult nucleus: Forms from birth on, these are secondary lens fibers, the outer cells are the newest (called the cortex), they are the least dense, have the lowest index of refraction. C. Transparency functions: 1. Structure 2. Shape 3. Arrangement of cells: Parallel to light rays. a. There are few nuclei on axis, mostly on equator. b. Method of suture termination will override location. 4. There is very little intercellular fluid, these cells are very dense. 5. No pigment: Does yellow with age. 6. Sodium/potassium balance: Prevents swelling by water. 7. Lack of hydration: No water gets out. 8. Arrangement of lens proteins: This is 33% of total weight of the lens. D. Opacities: Cataracts 1. Treatment is lens extraction which results in aphakia. a. Extracapsular surgery: Leave the posterior lens capsule in place, removal could damage the vitreous. b. Intracapsular surgery: All of the capsule is removed. c. Phacoemulsification: The lens is broken down by ultrasound and pieces removed by aspiration. 2. Intraocular implantation: Can be done in anterior or posterior chamber. 3. Caused by: Steroids, ultraviolet light, sugar shortage, age. 4. Physiology: 65% water, 35% protein. a. soluble proteins are highest in the cortex. b. When soluble proteins turn to insoluble proteins a cataract is formed. c. Cataracts have a high content of calcium ions.</text>
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<text>VII. Vitreous: A. Description: 1. Fills posterior 4/5 of globe's volume. 2. Adjacent to optic disc, retina, ora serrata, pars plana, space of Petit, posterior lens capsule ( space of Berger). 3. Patellar fossa: Cupshaped depression adjacent to lens. B. Features: 1. Anterior hyaloid surface: Anterior limiting layer, anterior to ora serrata. 2. Posterior hyaloid surface: Posterior limiting layer, posterior to ora serrata. C. Zones of the vitreous: 1. Cortex: Outermost a. Very thin: 100 micrometers (µm). b. Condensation of collagen fibers and hyaluronic acid form a mesh. c. Hyalocytes: Cells that are trapped in the cortex (probably WBC's, macrophages, and monocytes). 2. Intermediate zone: 99% water. a. More fluid, less hyaluronic acid and collagen than the cortex. 3. Central zone: Cloquet's canal, Hyaloid canal, Stillings canal. This is where the embryonic blood vessels were. a. Through center: Curved coneshaped zone. b. Attached on posterior lens at ringshaped Ligament of Weiger. 1. Ligament of Weiger: Hyaloideo capsular ligament, forms the space of Berger. c. Attached around optic disc. 1. Forms space of Martegiani. d. Made up of primary vitreous remnants of Cloquet's canal. e. During development it contains hyaloid blood vessel (artery). 1. Sometimes visible in adults. 2. Mittendorf dot: Residual blood vessel attached to posterior lens. This is very common. D. Areas of vitreous attachment: 1. Vitreous base: firmest attachment is over peripheral retina, ora serrata, and pars plana. a. Collagen fibers of cortex insert into internal limiting membrane of retina and ciliary body. 2. Posterior lens capsule: Ligament of Weiger (9 mm. diameter), breaks down with age. 3. Optic disc: Forms area of Martegiani. E. Functions of the vitreous: Mechanical support of the retina. F. Characteristics: 1. Transparent: 90% of all light passes through. Floaters are condensed fibers or debris in gel, usually related to aging. 2. Transmits light from 300 to 800 nanometers (nm.). 3. Cells in the vitreous: a. Hyalanocytes b. Slow diffusion of nutrients and metabolites. 1. Aqueous to vitreous. 2. Lens to vitreous. 3. Retina to vitreous. c. Hemorrhages are slow to leave, antibiotics are slow to get in. G. Vitrectomy: Removal of vitreous and replace with saline, the saline is eventually replaced by aqueous.</text>
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<text>VIII. Retina: A. Macular area of the fundus: (See diagram 4) B. Function of the retina: 1. Converts photons into nerve impulses. 2. Transmit signal to brain via optic nerve. 3. Sensory system: Vision occurs in the brain. C. Histology of the retina: 10 layers. (See diagram 5) 1. Cones: Daytime vision, photopic, color vision, 6 million cones in retina. 2. Rods: Low light vision, scotopic, 120 million rods in retina. 3. Function of rods and cones: Transduction of light into electrochemical energy, no action potential at this point.10 Retinal layers: 1. Retinal pigmented epithelium (RPE): a. Description: 1. Single layer of hexagonal cells. 2. Tightly cemented to choroid at inner layer of Bruch's membrane. 3. Cells joined by ZO, outer half of blood/retinal barrier. 4. Contains granules: a. Melanin: Inner 1/3 to 1/2 of cell (away from choroid). b. Lipofuscin: in residual bodies, undigested material, increases with age, throughout the cell. 5. Microvilli on inner side: Project closely around rods and cones, space between microvilli is filed with MPS. b. Function: 1. Phagocytosis and destruction of rod and cone outer segments, undigested part becomes lipofuscin granules, process is part of rod/cone renewal system. 2. Vitamin A metabolism: Vitamin A in segments of rods and cones change chemically as photo response. 3. Filters and controls metabolites to outer retina: ZO junctions between RPE cells. 4. Suppress light reflection: Pigment absorbs stray light. 2. Rod/cone layer (photoreceptor layer): a. Outer segment of rods and cones: 1. Stack of true membrane discs, (2 layers), lamellae. a. Disc contain visual pigment, rods (rhodopsin), protein, cones (red, blue, or green sensing) pigments are a piece of protein plus a piece of Vitamin A molecule. b. The pigment changes photochemically with light. 2. Rod renewal system: a. Discs constantly produced at inner end of outer segment. b. Discs migrate from inner end to outer end. c. Discs phagocytosed by PE cells at outer end when light is low. d. Found process through sequential dissection of animals provided with radioactive tracer amino-acids. b. Cilium: Connects outer and inner segment, area of flow from inner to outer. c. Inner segment: 1. Ellipsoid area, outer, contains mitochondria which provide the energy for disc formation. 2. Myoid area: Inner, Golgi vesicles filled with MPS. 3. Around myoid area are villons, processes of Muller's cells (fiber baskets of Schultze,these are Muller's cells that are pointing inward). 3. External limiting membrane (ELM): a. Line of attachment between cell types. 1. Photoreceptor cells to Muller's cells. 2. Muller's cells to Muller's cells. 3. Rarely, photoreceptor cells to each other. b. Desmosome and ZA attachments between cells, very strong and tight. c. Function: 1. Support retina. 2. Keeps cells in alignment. 4. Outer nuclear layer: a. Contains cell bodies of rods and cones, cytoplasm and nucleus. b. Outer fiber: From ELM to nucleus, short. c. Inner fiber: From nucleus to end of cell in outer plexiform layer, at inner end is cone pedicule or rod spherule which are specialized synaptic junctions. d. Cone nuclei are fewer and outer to rod nuclei. 5. Outer plexiform layer: (Outer molecular) a. Contains cone pedicules and rod spherules. b. Layer of synaptic connections: not one to one, very complex. 1. Rods/cones to bipolar cells. 2. Rods/cones to horizontal cells. 3. Horizontal cells to horizontal cells. 4. Horizontal cells to bipolar cells. 6. Inner nuclear layer: (See diagram 1) a. Characteristics of Muller's cells: 1. Cell processes extend from ILM past ELM (Fiber baskets of Schultze). 2. Contain glycogen: Metabolic and physical support. 7. Inner plexiform layer: Layer of synaptic connections. a. Bipolar to amacrine. b. Bipolar to ganglion. c. Amacrine to amacrine. d. Amacrine to ganglion. e. Amacrine to bipolar. (See diagram 2) 8. Ganglion cell layer: Cell bodies. a. Nucleus in ganglion cell layer, thickest at macular area. b. Dendrites to inner plexiform layer. c. Single axon in nerve fiber layer, transmits information from retina to lateral geniculate nucleus (LGN) of the brain. 9. Nerve fiber layer (NFL): Stratum Opticum. a. Ganglion cell axons: Nerve fibers. 1. Parallel to retinal surface. 2. Collect at optic disc. 3. Pass through lamina cribrosa. 4. Forms optic nerve. b. Papillo-macular bundle: Acuity, from fovea to temporal side of optic disc. c. Fibers from temporal periphery enter optic disc superior and inferior. d. Fibers from nasal periphery enter nasal side of optic disc. e. Cell types: 1. Astrocyte: In ganglion cell layer and NFL. 2. Microglia: Found in ganglion cell layer and NFL, could also be central nervous system macrophages (WBC's). 3. Retinal blood vessels. 10. Internal limiting membrane (ILM): MPS a. Basement membrane of glial cells (astrocytes, microglia, Muller's). b. Collagen fibers from vitreous cortex, very loose attachment.Summary: Convergent: 125 million photoreceptors converge into 1 million ganglion cells. Divergent: Each photoreceptor spreads out to several ganglion cells. (See diagram 3) D. Retinal blood supply: 1. Outer retinal blood supply is choriocapillaris: Supplies RPE to outer plexiform layer by diffusion. 2. Inner retinal blood supply: a. Central retinal artery (CRA): A branch of the ophthalmic artery. 1. Pierces optic nerve 10-12 mm. behind the eyeball. 2. Goes to center of optic nerve, enters eye at center of optic disc. 3. Divides near surface of optic disc into superior and inferior branches. 4. Divides at edge of optic disc into nasal and temporal branches. 5. Divides dichotomously proceeding to ora serrata. 6. Ends in capillaries called end arteries at ora serrata, loops around and joins to form the central retinal vein. (the end arteries themselves do not join). 7. Central retinal vein exits at center of optic disc. b. Characteristics: 1. Vessels travel in nerve fiber layer. 2. Capillaries are sent out to and including inner nuclear layer. 3. Plexus: Usually at random. a. Superficial: Ganglion cell and nerve fiber layers. b. Deep: Inner nuclear layer. 4. Capillary structure: a. Endothelial cells and basement membrane. b. ZO between endothelial cells, inner half of blood retinal barrier (not fenestrated). c. Outside basement membrane is interupted, layer of pericytes. 5. No retinal capillaries in center of anatomical fovea (just choriocapillaris). c. Cilio-retinal artery: From choroid at edge of optic disc to fovea, doesn't supply center of fovea (15-20% of the population have this). d. Outer plexiform layer blood supply is by diffusion from choriocapillaris and inner nuclear layer. This is where the two blood supplies meet (retinal and choriocapillaris).E. Regional organization: Maplike. 1. Foveola: a. .35 mm. diameter/.13 mm. thick (peripheral retina is .37 mm. thick). b. Contains 2500 closely packed cones resembling rods in shape. There are no rods present. c. Muller's cells separate to cones. d. Layers present are from RPE to OPL (Henle's fiber layer)and ILM. (six layers compared to ten). e. Inner fibers (axons) from cone cells leave foveola horizontally to form Henle's fiber layer. 2. Fovea: 100,000 cones. a. 1.5 mm. diameter. b. Depression in posterior pole. c. Mostly cones, rod free area is .57 mm. in diameter. d. Blood vessel free area is .50 mm. in diameter. e. Under the fovea, the choriocapillaris is thicker and the RPE cells are taller. f. Layers are picked up on the clivus. 3. Parafoveal region: a. .5 mm. band around the fovea. b. Mostly cones. c. Largest accumulation of nerve cells in the retina. Thick ganglion cell layer and inner nuclear cells pushed out of foveal area. d. Henle's fiber layer present and makes synapses. 4. Perifoveal region: a. 1.5 mm. band around parafoveal region. b. Ganglion cell layer is reduced from very thick to one cell thick. 5. Area centralis: The total area of parts 1 to 4 above (macula). a. 5.5 mm. in diameter. b. Center is foveola: .35 mm. temporal and 1 mm. inferior to optic disc. 6. Peripheral retina: Outside of macula. a. Rods are predominate.Summary:Cones: six million: 100,000 in fovea: acuity:photopic:color.Rods: 120 million: few in fovea: scotopic: black and white.(See diagram 4)F. Optic nerve: 1. Optic disc: a. Description: 1. No choroid, no retina, no scleral layers. 2. Composed of neuroglial cells and ganglion axons. 3. Color is white or yellow. 4. Surface is viewed by ophthalmoscope. 5. 1.5 mm. in diameter. b. Physiological cup: 1. Small round depression at center of optic disc. 2. Cup to disc ratio: Normal is .3, range from 0 to .9, larger cups (.7-.9) indicate pathology. 3. Cup depth. 4. Cup symmetry. 5. Scleral crescent: Temporal side of disc, white due to oblique scleral canal or edge of sclera not covered by retina or choroid. 6. Choroidal crescent: Accumulation of RPE or choroidal cells, dark ring, temporal side of disc. 7. Lamina cribrosa: Visible in deep cup. 2. Histology of optic disc and optic nerve: a. Internal limiting membrane of Elshnig: 1. Internal covering of disc. 2. Astrocytes and basement membrane. 3. Continuous with retinal internal limiting membrane, transition is at vitreal attachment(area of Martegiani). 4. If thickened at center of cup it is called the central meniscus of Kuhnt, astocytes are not always present. b. Intermediary tissue of Kuhnt: 1. Astocyte layer separating end of retina from optic nerve fibers. c. Border tissue of Jacoby: 1. Astrocyte layer separating marginal tissue of Elshnig from optic nerve fibers. 2. Continuous with intermediary tissue of Kuhnt. d. Marginal tissue of Elshnig: 1. Connective tissue separating sclera and choroid from border tissue of Jacoby. e. Lamina cribrosa: 1. Bundles of collagen connecting sclera across scleral canal. f. Optic nerve fibers: 1. Enter in pattern from retina. 2. Anterior to lamina cribrosa fibers join in 1000 fascicles of 1000 fibers each. Astrocytes surround fascicles. 3. At lamina cribrosa connective tissue separation is added. a. Maintain this conformation to optic chiasm. b. Between bundles are astrocytes and connective tissue, the astrocyte layer is called the septum. 4. At lamina cribrosa and posterior: Fibers are myelinated. a. Oligodendrocites: CNS myelinating cell. b. Each oligodendrocite myelinates several cells. c. If myelin continues anterior of lamina cribrosa a larger blind spot s formed (caused by developmental problems). 3. Covering (sheaths) of the optic nerve: a. Dura: Outer, tough and fibrous, collagen. b. Arachnoid: Middle, thin loose collagen and fibroblasts. c. Pia: Inner, thin, vascularized collagen and elastin, continuous with inner layers of sclera that surrounds fascicles. d. Subarachnoid space: Between arachnoid and pia, continuous with subarachnoid space of the brain, loose meshwork of collagen fibers filled with cerebrospinal fluid. Pathology: When intracranial pressure increase, pressure on optic nerve causes papilledema, edema at optic disc, blurred disc margins, swollen, shallow cup. Vision is usually normal. Blood flow to optic nerve and flow of nutrition from ganglion cell nucleus to dendrites restricted at bend into optic disc, resulting in the blurred margins and swollen, shallow cup, respectively. e. Between pia and nerve fibers is a layer of astrocytes. 4. Blood supply to optic nerve: a. Branches from pia pierce and supply most of optic nerve. b. Near optic disc, branches of the central retinal artery. c. Circle of Zinn/Haller: Outside of optic disc in sclera. 1. Branches into optic disc. 2. Circular blood vessel: Anastomoses of short posterior ciliary arteries. Circle of Zinn is a secondary function, primary is choroidal supply. d. Branches from choroid. e. Cilio-retinal artery: Choroidal supply to retina, usually circle of Zinn to retina, anastomoses of choroidal and retinal blood supply, not always present.</text>
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<text>IX. Periorbital Connective tissue: Fascia of the orbit, sheathing, binding, and partitioning. A. Description: 1. Continuous connective tissue covering. B. Functions: 1. Resisting initiation of ocular motion. 2. Braking of movements of eyeball. C. Components: 1. Orbital periosteum or periorbita: a. Inside of skull is lined with dura. b. At optic foramen, dura divides: 1. One layer is continuous with optic nerve sheath. 2. Outer layer is continuous with orbital periosteum. c. At the optic foramen both layers are continuous with the annulus of Zinn (tendenous ring, origin of rectus muscles). d. At the orbital rim the outer layer is continuous with facial bone periosteum. 2. Orbital septum or septum orbitale: a. Sheath of connective tissue from periosteum to orbital margin to edge of tarsal plates. b. Functions: 1. Prevents facial infection (preseptal cellulitis) from entering orbit (causing orbital cellulitis). 2. Prevents escape of orbital fat: Can be herniated with age. c. Lacrimal sac, obicularis, and most of eyelid are anterior to septum. d. Levator palpebrae is posterior to septum, tendons penetrate the septum. 3. Tenon's capsule: Fascia bulbi. a. Connective tissue covering of eyeball ending at limbus. b. Outer to episclera. c. Continuous with dural sheath of optic nerve. d. Pierced by blood vessels, nerves, and extraocular muscles. e. Eye is slightly movable in capsule, not a ball and socket. f. Barrier to infection passing between eyeball and orbit. 4. Epimysium (muscle sheaths): a. Connective tissue covering of extraocular muscles. b. Continuous with annulus of Zinn or periorbita at muscle origin. c. Continuous with Tenon's capsule at muscle insertion. d. Functions: 1. Carries blood vessels and nerves to muscles. 2. Encloses muscle fibers in one functional unit. 5. Check ligaments: Behind septum orbitale. a. Extension of muscle sheaths. 1. Medial: From sheath of MR to lacrimal bone. 2. Lateral: From sheath of LR to orbital tubercule of the zygomatic. 3. Inferior: From IR to eyelid, used for gaze level. 4. Superior: From SR to levator, used to raise lid in upward gaze. b. Functions: 1. Limit eyeball motion. 2. Coordinate eye and lid movements. 6. Suspensory ligament of Lockwood: a. Sling under globe from medial to lateral. b. Supports eye, even if maxillary bone is removed. c. Composed of parts of sheaths of IR, IO, and thickening of Tenon's capsule. 7. Palpebral ligaments: Laterally behind the septum orbitale, medially in front of septum orbitale. a. Bind ends of tarsal plates to bones. 1. Lateral: To orbital tubercule of zygomatic, posterior to orbital septum. 2. Medial: To maxillary bone, anterior to orbital septum. b. Functions: Holds tarsal plates to globe. 8. Orbital fat: a. Masses of fat enclosed in connective tissue. b. Zones: 1. Central fat: Inside muscle cones. 2. Peripheral fat: Outside muscle cones.</text>
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<text>X. Eyelids (palpebrae): A. Features: 1. Upper lid is larger. 2. Tarsal portion: Near margin, smooth close fit. 3. Orbital portion: Loose skin between tarsal and forehead or cheek. 4. Cilia: Eyelashes, 100-150 on upper, 50-75 on lower. 5. Pores of meibomian gland are inner to cilia. 6. Palpebral fissure: Opening between margins. 7. Canthus: Angle between eyelids, medial and lateral. 8. Lacrimal caruncle: In medial canthus, pinkish to white skin, may have hairs and glands. 9. Plica semilunaris or semilunar fold: Fold of conjunctival tissue, allows eye movement without stretching conjunctiva. 10. Lacrimal lake: Point of tear accumulation. (See diagram 1) B. Layers of the eyelid: Anterior to posterior. 1. Skin: a. Stratified squamous epithelium, sloughs off outer layers. b. Cornified, keratinized, toughened by proteins. c. Thin compared to rest of body. d. Ends at pores of meibomian glands. 2. Connective tissue: a. Areolar, loose, allows swelling in case of pathology or injury. 3. Muscles: a. Obicularis oculi: 1. Striated, closes eyelids. 2. Transverse band. 3. Connected at medial canthus to maxillary and frontal bones. 4. Temporal ends of fibers interdigitate at raphae. 5. Innervated by (VII) facial nerve. 6. Subcomponents: a. Muscle of Riolan:(pars ciliaris), at lid margin, separated from main band by lash follicles, its function is to keep margin near globe. b. Horner's muscle: (pars lacrimatis), at medial canthus, continuous with obicularis and Riolan's, goes to lacrimal bone and surrounds caniculi. Pulls tears from eye into caniculi. b. Levator palpebrae: 1. Striated, opens eyelid, if it fails ptosis results. 2. Origin: Annulus of Zinn and sphenoid bone. 3. Transverses apex of orbit over SR, tendons pierce septum and insert into skin of upper lid. 4. Innervated by (III) oculomotor nerve. 5. Gives rise to unstriated Muller's muscle of the eyelid, attached to tarsal plate, sympathetic innervation. 6. Levator and SR are attached to upper fornix. 4. Tarsal plates: a. Fibrous connective tissue. b. Tough, flexible, shape retaining. c. Hold eyelid against the globe. 5. Conjunctiva: a. Mucous membrane. b. Types: 1. Palpebral: Lines eyelids. 2. Bulbar: Covers globe to limbus. a. Both meet at fornix or cul-de-sacs. c. Meets skin at muco-cutaneous junction posterior to pores of the meibomian glands. d. Bulbar conjunctival epithelium is continuous with the corneal epithelium at the limbus. e. Layers of the conjunctiva: 1. Stratified columnar epithelium: Two layers thick at tarsal plate, 10-15 layers thick at limbus, not keratinized, has goblet cells. 2. Conjunctival stroma: Connective tissue with blood vessels which dilate with irritation, has lymphatic channels and lymphatic tissue, especially at fornix. 6. Glands: a. Goblet cells: Unicellular, produce mucous. b. Meibomian glands: Tarsal glands. 1. In tarsal plate. 2. Long multi-branched acini. 3. 25 in upper lid, 20 in lower lid. 4. Secrete oil (sebum): Outer layer of tear film. c. Zeis: Sebaceous, usually two per hair follicle. d. Moll: Sweat glands near hair follicles, less than one per follicle. e. Krause: Conjunctival. 1. Accessory lacrimal glands. 2. Subconjunctival. 3. 42 in upper fornix, 6-8 in lower fornix. f. Wolfring: 1. Accessory lacrimal glands. 2. Middle of lids at border of tarsal plate. 3. Upper lid has 2-5, lower has 2. C. Blood supply to eyelids: 1. Sources: Ophthalmic artery to medial palpebral artery, lacrimal artery to lateral palpebral artery, both supply their respective arcades. a. Peripheral arcade: Upper lid, middle height, between obicularis and levator. b. Marginal arcade: Upper lid, nearer to lash follicles in middle of lid thickness. c. Lower lid arcade: Near lash follicles. d. Arcades branch to rest of eyelid and anastomose. D. Sensory innervation: (See diagram 2) E. Lacrimal system: 1. Functions: a. Form a perfect optical surface on the cornea. b. Lubricate. c. Prevent infection through antibacterial substances (lysozymes). d. Moisten corneal and conjunctival surfaces. e. Supply oxygen to cornea. f. Remove sloughed off epithelial cells, dust and debris. 2. Components: a. Lacrimal gland: 1. Located in lateral upper orbit, small fossa in frontal bone (not in lacrimal fossa). 2. Regions: a. Large, orbital, superior. b. Small, palpebral, inferior: Divided by aponeurosis of levator. 3. Ducted to upper fornix by 10-12 ducts. 4. Flow is temporal to nasal, superior to inferior with each blink. 5. Secretes aqueous solution of salts and organic materials. b. Accessory lacrimal glands: 1. Glands of Krause. 2. Glands of Wolfring. 3. Lacrimal drainage system: a. Components: 1. Puncta: One in upper lid and one in lower lid, openings for flow into canaliculae. 2. Canaliculae: Passage from puncta to lacrimal sac, 2 mm. up and 8 mm. nasal, 90 bend called ampulla, slightly dilated here, walls are elastic and surrounded by Muller's muscle (behind sac). 3. Lacrimal sac: In lacrimal fossa (part of lacrimal and maxillary bones), anterior to septum orbitale, outside orbit 10-15 mm. long. 4. Nasolacrimal duct: Valved duct, most important is valve of Hasner at entrance to inferior meatus (lower end). 5. Inferior meatus in nose: b. Innervation of lacrimal gland: 1. Sensory: Trigeminal (V) nerve via lacrimal nerve. 2. Reflex secretion: Facial (VII) nerve, parasympathetic (dirt, sad, happy). 3. Blood vessels in lacrimal glands dilate with sympathetic innervation. (See diagram 3) 4. Tear film: a. Layers: 1. Inner: a. Mucous: Mucin, MPS and glycoproteins. b. Secreted by goblet cells in fornix. c. Wetting agent for epithelial cells and other layers of tear film. 2. Middle: 90% of film thickness (liquid layer). a. Lacrimal fluid: Aqueous layer, tear layer. b. Secreted by lacrimal gland, Krause and Wolfring, c. Composition: 1. Ions: Sodium, potassium, chloride. 2. Glucose. 3. Urea. 4. Proteins: Albumin, globulin, lysozyme. d. Quantity: 1.2 microliters per minute (µl/min.) production, 50µl equals one drop. 3. Outer layer: a. Oil: Sebum, sebaceous, lipid. These are cholesteroles, lecithin, and fatty acids. b. Main producers are the meibomian glands, secondary are the Zeis. c. Functions: 1. Prevent tear evaporation. 2. Prevents tears from overflowing onto lids. b. Blink: 1. Spreads tear layers evenly. 2. Breakup time (BUT) should be greater than 10 seconds. c. Tear elimination sequence: 1. Close lids: a. Eyelid margins move nasally forcing tears toward lacrimal lake. b. Puncta are aligned with lacrimal lake. c. Canaliculae are compressed by Horner's muscle. 2. Open lids: a. Canaliculae open creating a negative pressure. b. Tears are sucked into canaliculae. 3. Close lids: a. Tears in canaliculae are squeezed into lacrimal sac, puncta close somewhat acting as a valve to prevent backup or retrograde. b. Further passage is passive, with valves preventing any backup.</text>
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<text>XI. Extraocular muscles: (EOM) A. General description: 1. Feedback loop: Light falls on retina, blurry, correct gaze with EOM, vision clears. 2. Directions of gaze: a. Primary position: Head held normally, eyes focused at infinity, cornea centered in palpebral fissure. b. Duction: Movements of one eye: 1. Adduction: Nasally. 2. Abduction: Temporally. 3. Elevation: Sursumduction, upward. 4. Depression: Deorsumduction, downward. 5. Intorsion: Rotation around visual axis, top of eye rotates nasally. 6. Extorsion: Rotation around visual axis, top of eye rotates temporally. c. Version: Movements of two eyes: 1. Convergence: Both adduct. 2. Divergence: Both abduct. a. Above two are vergences, eyes move opposite directions. 3. Levoversion: Both to left gaze. 4. Dextroversion: Both to right gaze. 5. Sursumversion: Both elevated. 6. Deorsumversion: Both depressed. a. Above four are versions, both eyes move in same direction. B. Characteristics of EOM: Motor unit muscles. 1. Striated. 2. Rich nerve supply, 7 muscle fibers per neuron (skeletal muscles have 10-100 fibers per neuron), fine, fast, precise. C. Rectus muscles: Four of them. 1. Characteristics: a. Lie in the four quadrants of the eyeball. b. Origin is annulus of Zinn. c. Insertion into sclera 5 to 8 mm. from limbus. (See diagram 1) 2. Medial rectus: a. Adduction: Lies in same plane as optic axis. b. Thickest and most powerful. c. Innervation by oculomotor (III) nerve, inferior division. d. Convergence of eye for nearpoint focus. e. Best developed check ligament. 3. Lateral rectus: a. Abduction: Lies in same plane as optic axis. b. innervation by abducens (VI) nerve. 4. Superior rectus: a. Lies above superior oblique. b. Insertion oblique to optic axis by 23 degrees. c. Elevation, adduction, intorsion. d. Innervation by oculomotor (III) nerve, superior division. 5. Inferior rectus: a. Lies below inferior oblique. b. Insertion oblique to optic axis by 23 degrees. c. Depression, adduction, extorsion. d. Innervation by oculomotor (III) nerve, inferior division. e. Muscle sheath contributes to ligament of Lockwood. D. Oblique muscles: Two of them. 1. Superior oblique: a. Origin: Lesser wing of the sphenoid above and medial to the optic foramen. b. Tendon passes through trochlea and turns posterior. c. Insertion into sclera under superior rectus. d. Trochlea: In superior nasal corner of orbit on frontal bone. e. Angle of action is 51 to 53 degrees from visual axis. f. Depression, intorsion, abduction. g. Insertion is primarily in posterior, superior, temporal quadrant. h. Innervation by trochlear (IV) nerve. 2. Inferior oblique: a. Origin at anterior medial floor of orbit on maxillary bone. b. Runs posterior and lateral under LR. c. Insertion posterior, inferior, temporal quadrant, under macula. d. Angle of action is 51 to 53 degrees from visual axis. e. Elevation, extorsion, abduction. f. Muscle sheath contributes to ligament of Lockwood. g. Innervation by oculomotor (III) nerve, inferior division. (See diagram 2) E. Motion: 1. All muscles have constant tone, to move causes tone to increase or decrease. (See diagram 3) (See diagram 4)</text>
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<text>XII. Blood supply to the brain, eye, and orbit: A. Introduction: 1. Constant blood supply to brain and eye is required, CNS tissue has high metabolic rates, but cannot store energy, cannot use anaerobic metabolism, loss of blood supply (ischemia) causes nueronal death in minutes. 2. Vascular diseases: Interupted blood supply. a. Hypertension. b. Atherosclerosis: Hardening of the arteries. B. Vertebral blood supply to brain: 1. Aorta to subclavian to 2 vertebrals to basilar. 2. Vertebral arteries enter cranium through foramen magnum and combine into basilar. 3. Branches of basilar artery to brain. a. Posterior cerebral arteries: Serve LGN, visual cortex, posterior optic radiations, and superior colliculus. b. Superior cerebral arteries: Serves superior colliculus. (See diagram 1) C. Internal carotid supply to the brain: 1. (See diagram 2) 2. Branches of the internal carotid: Five of them. a. Anterior cerebral: One from each internal carotid, joined near chiasm by anterior communicating artery, serves chiasm and intracranial optic nerve. b. Ophthalmic: Supply to eye. c. Middle cerebral: Largest branch of the internal carotid, this artery is the most critical for stroke patients, serves chiasm, optic tract, optic radiations, visual cortex. d. Anterior choroidal: Serves chiasm, optic tract, LGN, beginnings of the optic radiations. e. Posterior communicating: Anastomoses of carotid and vertebral system. D. Circle of Willis: (See diagram 3) 1. Most brains do not have a complete circle of Willis. 2. The circle is completed by the anterior and posterior communicating arteries. 3. Provides alternative blood supply to brain: Vertebral and carotid. E. Venous return from brain: 1. Parallels arteries of brain. 2. Veins drain into sinuses: Venous channels formed by splitting of the dural lining of the skull. (See diagram 4) 3. Cavernous sinuses: a. Two sinuses on floor of skull, formed by the splitting of the dura matter, very large. b. Flows into jugular vein. c. Receives blood from ophthalmic vein. d. The internal carotid artery runs through the cavernous sinus from skull entry to branch point. e. Cranial nerves (III),(IV),(V),(maxillary and ophthalmic), and (VI) run through the walls of the cavernous sinus. f. Blockage of blood in the sinus puts pressure on the structures within the sinus. 1. Thrombus: Clot, puts pressure on structures. a. Less blood to brain from internal carotid. b. Paralysis of extraocular muscles (III,IV,VI). c. Loss of sensory input from (V),(maxillary and ophthalmic). F. Ophthalmic artery: Total blood supply to eye and orbit. 1. Characteristics: Coiled. a. Branch of internal carotid. b. Enters optic foramen with optic nerve. c. tortuous: For mobility of the eye, clotting at bends are dangerous. d. Parallel pair of veins leave orbit at orbital fissure (no valves). 2. Branches of the ophthalmic artery: a. Central retinal artery (CRA): 1. Branches off near optic foramen. 2. Runs below and close to optic nerve, enters 10 to12 mm. behind eyeball (half of the intraorbital distance of the optic nerve), runs through the center of the optic nerve, through the lamina cribrosa, right angle at surface of optic disc. 3. Branches in retina: Superior and inferior then nasal and temporal, loops back at ora serrata forming central retinal vein (CRV) at center of optic disc, leaves optic nerve 10 to12 mm. behind eyeball, drains into superior ophthalmic vein or cavernous sinus. 4. Use of ophthalmoscope: a. Arteries are brighter red. b. Arteries have a light streak in the middle (arterial light reflex). c. Arteries are usually smaller than veins. d. Capillaries from CRA do not supply foveola. e. No sphincters in retinal arterioles, flow is controlled in capillary beds to maintain blood oxygen levels. f. Near ora serrata the end arteries loop back to the venous system, degeneration of these end arteries with age cause peripheral cystoid degeneration. b. Short ciliary arteries: 8 to 18 of them branch from ophthalmic. 1. Enter through sclera in a ring around optic nerve. 2. Choroidal blood supply: Branch anterior and inner and form choriocapillaris. 3. Choriocapillaris: Haller's and Sattler's layer, wide-bore, fenestrated, serving outer retinal layers (PE cells, photoreceptors and foveola). 4. Some branches anastomse to form circle of Zinn, blood supply to optic disc. 5. Cilio-retinal artery: Can join choroidal and retinal blood supply usually from circle of Zinn, only present in about 15% of the population. c. Long posterior ciliary arteries: 1. Two branches, enter sclera at each side of optic nerve outside circle of short ciliary arteries. 2. Run through suprachoroid to anterior eye. 3. At anterior eye they divide into superior and inferior branches, all anastomose with anterior ciliary arteries to form major circle of iris, just inner to Muller's muscle of the ciliary body. 4. Major circle branches to radial arteries of iris and to most of the ciliary body. 5. Before formation of major circle there are recurrent branches to anterior choriocapillaris. 6. Drainage from choroid is non-parallel, four vortex veins in all four quadrants, the two superior vortex veins drain into the superior ophthalmic vein, the two inferior vortex veins drain into the inferior ophthalmic vein. d. Muscular arteries: 1. Wolff's description: Two large muscular arteries. a. Lateral: Branch of lacrimal artery, serves LR, SR, SO, and levator. b. Medial: Branch of ophthalmic artery, serves MR, IR, IO. 2. Alternative explainations: 4 muscular arteries. a. I.: Branch from lacrimal artery, serves LR. b. II.: Branch from supraorbital artery, serves SR, SO, levator through supraorbital foramen. c. III.: Branch from ophthalmic artery, serves MR. d. IV.: Branch from infraorbital artery, serves IR, IO, leaves through infraorbital foramen. e. Anterior ciliary arteries: 7 of them. 1. Branches from muscular arteries. 2. Reach eye along tendons of rectus muscles. 3. Pierce sclera and join major circle, then anastomose with long posterior ciliary arteries. 4. Before piercing sclera, branch anteriorly to make up episcleral plexus at limbus, limbal loops, and conjunctival plexus. 5. Also sends recurrent branches to choroid. f. Lacrimal artery: 1. A direct branch of the ophthalmic artery. 2. Lateral side of orbit. 3. Supplies LR, lacrimal gland, branches to connective tissue in optic nerve (pia), anterior to serve eyelid via lateral palpebral artery (3 arcades). 4. Supplies temple area via zygomatic artery. g. Supraorbital artery: 1. Branches off above optic nerve, goes above eye and muscles. 2. Serves forehead, SR, SO, levator, leaves orbit through supraorbital foramen. h. Anterior and posterior ethmoidal arteries: 1. Exits orbit through ethmoidal foramen, supplies ethmoid sinus and nose. i. Supratrochlear artery: 1. Exits orbit through septum orbitale. 2. Serves orbicularis, corrugator, and skin of forehead. j. Dorsal nasal artery: 1. Serves nasal mucosa, lacrimal sac, skin of nose. 2. Penetrates septum orbitale exiting orbit. k. Medial palpebral artery: Branch of dorsal nasal artery. 1. Three (3) branches or arcades to medial eyelid. 2. Also serves caruncle and plica semilunaris.(See diagram 5)(See diagram 6) Summary of ophthalmic artery: 1. Lateral side of orbit: Lacrimal artery. 2. Medial side of orbit: Direct branches from ophthalmic. 3. Upper side of orbit: Supraorbital artery. 4. Lower side of orbit: Infraorbital (not a part of the ophthalmic artery system). G. Venous drainage of the eye and orbit: 1. Superior ophthalmic vein: a. Receives blood from upper half of eye, orbit, and lids. 1. Superior vortex veins (2). 2. Superior muscular veins (two from the SR and MR, one from the LR, and one from SO). 3. Venous arcades from eyelids, some go to face. 4. Central retinal vein (CRV). b. Leaves orbit by superior orbital fissure to cavernous sinus. 2. Inferior ophthalmic vein: a. Receives blood from lower half of eye, orbit, and lids. 1. Inferior vortex veins (2). 2. Inferior muscular veins (one from IO, two from IR). 3. anterior ciliary veins: 14 of them. a. Two for each anterior ciliary artery. b. Fed from three sources: 1. Anterior ciliary plexus in anterior ciliary body. 2. Episcleral plexus, includes aqueous from Schlemm's canal. 3. Limbal loops. 4. These drain into the muscular veins. H. Summary of Circulation: 1. Retina: a. Inner: Central retinal artery and vein. b. Outer: Short posterior ciliary arteries (choriocapillaris). 2. Choroid: a. Primary: Short posterior ciliary arteries. b. Anterior secondary: Anterior ciliary arteries, long posterior ciliary arteries. 3. Iris: a. Major circle of the iris: Anterior ciliary arteries, long posterior ciliary arteries. 4. Lens: a. No blood supply, served by aqueous. 5. Conjunctiva and eyelids: a. Medial: Medial palpebral artery from ophthalmic. b. Lateral: Lateral palpebral artery from lacrimal. c. At limbus, conjunctiva: Anterior ciliary arteries. 6. Cornea at limbus: a. Anterior ciliary arteries. 7. Sclera: a. Avascular, some small branches of the long posterior ciliary arteries. 8. Extraocular muscles: a. SR and SO: Supraorbital artery. b. MR: ophthalmic artery. c. LR: Lacrimal artery. d. IR and IO: Infraorbital artery. I. Lymphatics: 1. No lymphatic system in the eyeball itself. 2. Eyelids and conjunctiva: a. Lateral: Preauricular lymph nodes. b. Medial: Submandibular lymph nodes.The circulation overall summarized: About three forths of the blood supply to the eye and orbit is supplied by the ophthalmic branch of the internal carotid artery. The remainder is supplied by a branch of the external carotid artery. Most of the veins draining the orbital area empty in to the cavernous sinus and the internal jugular vein. The rest drain into the pterygoid plexus and the external jugular vein.Extraocular structures: Most of the extraocular structures derive blood from the ophthalmic artery, a vessel which arises from the internal carotid artery. The ophthalmic artery enters the orbit through the optic foramen lateral to the optic nerve. Normally it passes over the nerve as it branches to supply the orbit and globe. Three main branches of the ophthalmic artery, the lacrimal, supraorbital, and medial branch, supply the lateral, upper and medial structures of the orbit, respectively. The lacrimal artery sends branches laterally and above to the lateral rectus and sometimes to the superior rectus muscles, to the lacrimal gland, and to both lids. A recurrent meningeal branch passes back through the superior orbital fissure to the brain. Branches from the supraorbital artery supply the superior rectus, the levator, and superior oblique muscles, the forehead and upper lid, and often the lacrimal gland. The true continuation of the ophthalmic artery is its medial branch which supplies the medial rectus muscle and may send branches to neighboring extraocular muscles. It gives off the frontal artery to the forehead and upper lid, as well as the dorsal nasal artery to the lids and lacrimal sac. The ethmoid arteries pass through the ethmoidal foramina and are not involved in the circulation of the eye. The lower portion of the orbit is supplied by the infraorbital artery. A continuation of the pterygopalatine branch from the internal maxillary and external carotid system, the infraorbital artery enters the orbit through the inferior orbital fissure. Branches of the inferior artery supply the inferior rectus and the inferior oblique muscles, the lower lid, the lacrimal sac and duct, and the lacrimal gland. The infraorbital artery then continues into the infraorbital canal. (See diagram 7)The veins of the orbit: The orbital contents are drained primarily by the superior and inferior ophthalmic veins. The larger superior ophthalmic vein drains those areas supplied by the branches of the ophthalmic artery, that is, the nasal, upper and temporal portions of the orbit. Thus it receives the veins from all of the extraocular muscles except the inferior rectus and inferior oblique. The superior ophthalmic vein leaves the orbit via the the superior orbital fissure and empties into the cavernous sinus which in turn drains into the internal jugular vein. A smaller vessel, the inferior ophthalmic vein drains the lower portion of the orbit. It originates with a network of veins at the front part of the floor and medial wall of the orbit and drains those areas supplied by the infraorbital artery, including the muscular veins of the inferior rectus and inferior oblique. The inferior ophthalmic vein usually leaves the orbit in two divisions. One branch descends through the inferior orbital fissure of the pterygoid plexus, with eventual drainage into the internal maxillary, internal jugular and external jugular veins. The other branch of the inferior ophthalmic vein usually passes through the superior orbital fissure joining the superior ophthalmic vein before it enters the cavernous sinus.The lids and conjunctiva: Circulation of the lids and conjunctiva is complex and varied and is derived from the vessels that supply the face, as well as those that supply the orbit. However, most of the palpebral blood supply derives from branches of the ophthalmic artery. Laterally the lacrimal artery supplies the lateral palpebral arteries to the upper and lower lids. Medially, the dorsal nasal artery from the ophthalmic, supplies the upper and lower medial palpebral arteries. These arteries join to form the palpebral arcades in the lids, the pattern being less distinct in the lower lid. The veins of the lids have a similar arcaic pattern. Medially they drain into the angular vein, then either to the superior ophthalmic vein through the orbital veins, or to the anterior facial vein. Laterally they empty into the anterior facial vein and superficial temporal vein. The palpebral arcades also supply most of the arteries to the conjunctiva, including the palpebral conjunctiva, the fornices, and the bulbar conjunctiva, up to four millimeters from the limbus. Most of the conjunctival veins drain into the veins of the upper and lower lids. Near the limbus though, the deeper veins drain to the anterior ciliary veins of the globe.Supply to the globe: The globe is supplied largely by the ophthalmic artery and its branches, which form two independent circulatory systems within the globe. The retinal system supplies the inner layers of the retina only and the choroidal or ciliary system supplies the rest of the globe. The retinal system consists of the central retinal vessels and their branches. The retinal artery is the first branch to arise from the ophthalmic artery at the apex of the orbit. It enters the optic nerve between 7 and 15 millimeters behind the globe accompanied temporally by the central retinal vein. The course of the vessels in the retina can easily be seen using an ophthalmoscope. The artery and vein immediately divide into upper and lower branches as they appear towards the nasal side of the optic disc. Fluorescein angiography clearly demonstrates further branching of these vessels to provide the blood supply to the entire retina. The arterial branches end in capillaries which do not anastomose with any other system of vessels. The pattern formed around the macula is similar to that formed by the nerves. The capillaries of the CRA do not anastomose with any other system of vessels upon leaving the globe. The CRV usually drains into the cavernous sinus with an anastomic branch to the superior ophthalmic vein, or rarely into the inferior ophthalmic vein. The retinal artery and vein serve all portions of the retina except a layer of rod and cone cells which are supplied by the choroidal circulation.The choroidal or ciliary circulation: The ciliary system supplies the choroid, the ciliary body, the iris, the cornea and the structures near the limbus. This circulation is composed of an anterior and a posterior system of arteries and veins which interconnect in the ciliary body (the major circle of the iris). The posterior ciliary arteries arise in a variable pattern from the ophthalmic artery and run parallel to the optic nerve toward the globe. Two long posterior ciliary arteries, temporal and nasal, and about 20 short posterior ciliary arteries are usually present. A few of the short arteries anastomose to form the circle of Zinn within the sclera around the optic nerve and supply the nerve head. Most of the short arteries pass into the globe where their many branches, along with those of the veins, comprise the choroid. The two long posterior ciliary arteries run in the sclera and suprachoroidal space directly to the ciliary body where each artery divides into a superior and inferior branch. These four branches anastomose in the anterior part of the ciliary body to form part of the great arterial circle (major circle of the iris). At this point the anterior ciliary arteries enter the eye to supply most of the anterior part of the globe. The seven anterior ciliary arteries spring from the arteries of the four rectus muscles at their insertions. The inferior, medial and superior rectus arteries supply two anterior ciliary arteries each, while the lateral rectus artery gives off one. The anterior ciliary arteries run in three general directions. Some of the smaller branches run forward toward the canal of Schlemn, the cornea and conjunctiva. Larger recurrent branches are sent backward to the ciliary muscle and to the choroid. Large branches also descend straight into the anterior part of the ciliary body. These straight branches join with the branches of the long posterior ciliary arteries in the arterial circle. The arterial circle lies just behind the base of the iris and supplies arteries to the iris which run radially toward the pupil. A few of these vessels divide before reaching the pupillary margin and form an incomplete ring known as the minor circle of the iris. The normal cornea does not contain blood vessels, but receives its supply from the capillaries derived from the anterior branches of the anterior ciliary arteries. The primary system of venous drainage from the uveal tract is the posterior or vortex system. From the iris and most of the ciliary body the vessels pass backwards to join the veins of the choroid. From the choroicapillaris to the outer portions of the choroid progressively larger vessels are formed which begin to assume circular or vortex configurations within the choroid. Four large vortex veins finally emerge, one from each quadrant of the choroid and leave the globe some five to eight millimeters behind the equator. The upper two vortex veins drain into the superior ophthalmic vein and the lower two drain into the inferior ophthalmic vein. The anterior ciliary system of veins drain the most anterior and outer portions of the globe, that is, the areas near the limbus. These areas include the anterior and outer portion of the ciliary body, the canal of Schlemn, and the cornea. The veins from the outer part of the ciliary body, or the anterior ciliary plexus, as well as twenty or more aqueous veins from the canal of Schlemn drain to an intrascleral veinous plexus which in turn drains into the episcleral plexus. At the corneal limbus the capillary arteries that supply the cornea bend backwards forming the limbal loops at which point they become the corneal veins which drain directly into the episcleral plexus. From the episcleral plexus, the anterior ciliary veins (about 14 in all) run to the insertion of the rectus muscles to drain into the muscular veins. The anterior ciliary veins thus follow the same pattern as the anterior ciliary arteries except that the veins are twice as numerous. The veins from the inferior rectus and inferior oblique muscles then join the inferior ophthalmic vein. Blood from the rest of the muscular veins drains into the superior ophthalmic vein and flows through the cavernous sinus and into the internal jugular vein.(See diagram 8)</text>
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<text>XIII. Embryology: A. Three basic germ tissue layers: Outer to inner. 1. Ectoderm: CNS and skin. a. Surface ectoderm: Lens, eyelids, glands, cilia, corneal epithelium, conjunctival epithelium, lacrimal gland. b. Neural ectoderm: Ten retinal layers, optic nerve, neuroglia (except microglia), ciliary body epithelium, iris muscles. 2. Mesoderm: Blood vessels, connective tissue, muscles, bones. a. In the eye: Blood vessels, choroid, sclera, ciliary muscle, ciliary body, iris stroma, corneal stroma, conjunctival stroma, extraocular muscles, orbital bones, eyelid muscles, tarsal plates. 3. Endoderm: Lining of GI and respiratory tracts. a. There is no endoderm in the eye. B. Early development: 1. At twenty days: Ectodermal plate folds, the inside is neural ectoderm and the outside is surface ectoderm, forms the optic pit which invaginates and fuses to form optic vessicles (about 24th day), optic stalk begins to form. C. Optic cup formation: 1. At twenty eight days: Invagination in outer direction forms optic cup, opening between sides is the choroidal fissure which closes from top down to lower nasal and fuses about 35 days. Coloboma results when fissure fails to close completely, usually inferior and nasal. D. Lens formation: 1. Also at twenty eight days: Surface ectoderm invaginates and forms the lens placode, contact with neural ectoderm is needed to form lens, a single cell vesicle is formed separated from the surface ectoderm. 2. At forty two days: Posterior cells extend longitudinally, fill vesicle space and form the primary lens fibers which becomes the spherical embryonic lens nucleus. 3. From forty five days to birth: Secondary lens fibers are formed by mitosis making up the fetal nucleus with "Y" sutures (anterior "Y" suture is erect). 4. After birth: Complex "Y" sutures are formed. 5. At the lens vesicle stage: The epithelial cells secrete the lens capsule prior to formation of the fetal nucleus. E. Blood system: 1. Hyaloid artery to tunica vasculosis lentis: a. Atrophy at three months: Glial tissue may remain. 1. Remnants may be seen in Cloquet's canal. 2. At optic disc: Mittendorf dot, Bergmeister papilla, area of Martegiani. 3. Hyaloid artery becomes central retinal artery. F. Retinal development: 1. Outer layer of central area of optic cup becomes RPE. 2. Inner layer becomes nine layers of the retina. 3. Foveal development is complete after about 4 to 6 months. G. Iris/Ciliary body: 1. Anterior epithelium: Pigmented myoepithelial cells (dilator muscle). 2. Posterior epithelium: Single layer of pigmented cells. 3. Sphincter breaks off of anterior epithelium before pigmentation develops. 4. Inner and outer layers of the optic cup also form the inner (non-pigmented) and outer ( pigmented) ciliary body epithelium. 5. The rest is mesodermal. H. Vitreous: 1. Primary: Third to sixth week the optic cup is filled with vitreous from three sources: a. Inner layer of optic cup (neural ectoderm). b. Secretions from lens vesicles (surface ectoderm). c. Mesodermal cells in center of cup. 2. Secondary: About six weeks. a. Primary source is neural ectoderm. b. Pushes primary vitreous to center of Cloquet's canal. 3. Tertiary: Ten to eleven weeks. a. Formation at zonule fibers.I. Summary: 1. Lens: Surface ectoderm. 2. Sclera: Mesoderm. 3. Iris: a. Neural ectoderm: Ant. and post. epithelium, sphincter, dilator. b. Mesoderm: Stroma and ant. border layer. 4. Ciliary body: a. Neural ectoderm: Inner and outer epithelium. b. Mesoderm: Stroma, ciliary muscle, supraciliaris. 5. Cornea: a. Surface ectoderm: Epithelium and basement membrane. b. Mesoderm: Stroma, Bowman's, endothelium, Descement's. 6. Conjunctiva and skin: Surface ectoderm.</text>
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<text>XIV. Efferent nervous system: A. (See diagram 1) 1. Parasympathetic: a. From CNS to iris sphincter and ciliary body. 1. Preganglionic fibers originate in the Edinger Westphal nucleus (Accessory III nucleus) in the tegmentum at the level of the superior colliculus (mesencephalon). 2. Fibers travel in III. nerve through superior orbital fissure, follow inferior branch of III. nerve, branch off and form motor root of of the ciliary ganglion. 3. Fibers synapse in ciliary ganglion. 4. Postganglionic fibers via short ciliary nerves in suprachoroid to anterior eye, ciliary muscle and iris sphincter. b. From CNS to lacrimal gland (increased tear film): 1. Preganglionic fibers from lacrimal nucleus in the pons, join sensory root of VII. nerve, pass through facial ganglion (no synapse), enter great petrossal, join with deep petrossal nerve to form the vidian nerve, enters sphenopalatine ganglion and synapses. 2. Postganglionic fibers enter zygomatic branch of maxillary V. nerve, a mixed nerve, connecting branch to lacrimal nerve, terminates in the lacrimal gland. 2. Sympathetic: a. Preganglionic fibers originate in cervical 18 (C-18) to thoracic 3 (T-3) vertebrae. Come out of ventral roots of the spinal cord. Go superior, to superior cervical ganglion in neck and synapse. b. Postganglionic fibers run up neck into skull on wall of internal carotid artery and branch in skull. 1. Branch I.: Through gasserian ganglion to ophthalmic V. to nasociliary nerve to long ciliary nerve to dilator muscle. 2. Branch II.: Sensory root of ciliary ganglion to short ciliary nerves to blood vessels of choroid (vasoconstriction). 3. Branch III.: Through deep petrossal nerve to vidian nerve through sphenopalantine ganglion to zygomatic nerve to lacrimal gland (vasodilation). 4. Branch IV.: Via oculomotor III. nerve superior branch to levator to Muller's muscle of eyelid. c. Pathology: 1. Horner's syndrome: Trauma at the level of the superior cervical ganglion, damages sympathetic system, causes miosis, ptosis, and anhydrosis, usually unilateral. 3. Summary of ocular reflex pathways: a. Direct/consensual pupillary response: 1. Afferent: Retina to pretectal nuclei. 2. Intracranial: a. Tectotegmental tract: From pretectal to EW nucleus on same side. b. Posterior commissure: Crossover from pretectal to opposite EW nucleus. The pretectal nuclei are not connected. 3. Efferent: EW to iris sphincter. a. Preganglionic fibers follow III. nerve to ciliary ganglion and synapse. b. Postganglionic fibers go to sphincter via short posterior ciliary nerves ( parasympathetic). b. Accommodation/convergence pupillary response: 1. Near response or reflex: Ciliary muscle contracts, medial recti contract, sphincter contracts (accommodation, convergence, miosis). 2. AC/A: Ratio between accommodative convergence and amount of accommodation, usually 3.5 diopters. 3. Ways to separate accommodation/convergence/pupil: a. Presbyopia: Accommodation = zero, AC/A increases. b. Mydratic (sympathomimetic): Affects dilator muscle, no pupillary response. c. Cycloplegic (parasympatholytic): Blocks innervation to ciliary and sphincter muscles, convergence without accommodation or miosis. 1. Afferent pathway: Visual pathway to 17. 2. Intracranial: 17 to 18,19,22 to midbrain to EW and III. nerve nucleus. 3. Efferent: a. Autonomic (parasympathetic) to EW to iris sphincter and ciliary muscle. b. Somatic: III. nucleus to medial rectus. c. Pathology: 1. Argyll Robertson pupil: Loss of direct and consensual response with retension of near point miosis, results from lesion after branch off to optic tract to EW nucleus. a. Can be unilateral or bilateral. b. Remember that the near response goes directly to EW, but direct/consensual goes to the pretectal first. (See diagram 2) d. Example lesions: 1. Sever optic nerve of left eye: a. Direct: left no, right yes. b. Consensual: left yes, right no. 2. Damage to fibers of left optic nerve: a. Loss of direct in left eye. b. Swinging flashlight test more sensitive than fields. c. Called Marcus Gunn or Relative afferent pupillary defect (RAPD). 3. Saggital section through chiasm: a. Bitemporal hemianopsia. b. Pupillary response unaffected. 4. Section left optic tract: a. Right homonymous hemianopsia. b. Pupillary response unaffected. 5. Cut after LGN, but before superior brachia: a. Right homonymous hemianopsia. b. Pupillary response unaffected. 6. Cut fibers from both PT to one EW: a. Argyll Robertson in one eye on affected EW. 7. Cut both PT to both EW: a. Argyll Robertson on both eyes. b. Associated with tertiary syphillus, tumor, hemorrhage. 8. Cut III. nerve: a. Droopy lid and slight abduction, ipsi. b. Motor loss from MR, SR, IR, IO, levator. c. Parasympathetic loss of sphincter and ciliary body. d. No pupillary response, no accommodation, no miosis on ipsilateral side. 9. Postganglionic fiber damage: a. Loss of ciliary body and sphincter. b. Loss of choroidal blood vessels and dilator. 10. Adie's tonic pupil: Affects postganglionic fibers, after ciliary ganglion, after they branch from III. nerve. a. Eye movements are normal. b. Pupillary responses are slow or absent. c. Accommodation is hindered. 4. Trigeminal or corneal reflex: a. Corneal pain results in lacrimation, blinking and miosis. (See diagram 3) 5. Sleep reflex: a. Parasympathetic system takes over and miosis results. 6. Role of the superior colliculus: a. In other animals: Visual reflex system. b. In man: Integration of eyes, ears, head, trunk, and limbs to fixate on a visual target. c. Connections to superior colliculus: 1. Afferent: (going to): a. A few from the optic tract. b. From cortex area 17, 18, 19 via the optic radiations. c. From the spinal tectal tract. 2. Efferent: a. Oculomotor nuclei. b. Through tectal spinal tract. c. Moves head and neck. B. Somatic system: Eye movements. 1. Oculomotor nucleus: In tegmentum at the level of the superior colliculus in mesencephalon, adjacent to the EW nucleus (parasymp.), each muscle innervated has a section in the III. nerve nucleus. a. Oculomotor nerve (III.) contains fibers from the III. nerve (somatic) and fibers from the EW (parasymp.). 1. Superior branch: SR and levator. 2. Inferior branch: MR, IR, IO, and motor root of ciliary ganglion. 2. IV. nucleus: In tegmentum at level of the inferior colliculus in midbrain. a. Trochlear nerve (IV.): Innervates SO. 3. VI. nucleus: In tegmental portion of the pons in midbrain. a. Abducens nerve (VI.): Innervates LR. 4. Medial longitudinal vasiculus: Coordinates eye movements, for balance, connects III., IV., VI. and vestibular nuclei (VIII.). 5. Supranuclear control mechanisms: a. Smooth tracking or pursuit, maintains image on fovea, fixation movements. b. Rapid eye movements, saccadic, usually involuntary, originates in contralateral frontal eye fields (8), stimulus on one side produces contralateral conjugate eye, head, and neck movements.XV. Innervation of the eye: A. Definitions: 1. Neuron: Nerve cell. 2. Synapse: Junction between nerve cells. 3. Nervous system: Sequence of neurons connected by synapses. 4. Neuroglia: Support cells among neurons. 5. Myelin: Fatty sheath surrounding most nerve fibers, (myelinated = medullated). 6. Nucleus: Group of neuron cell bodies in CNS with common connections/functions. 7. Tract: Group of nerve fibers running together from one part of CNS to another part of the CNS. 8. Ganglion: Group of nerve cell bodies outside of the CNS. 9. Information into CNS: Sensory-afferent-centripetal. 10. Information out of CNS: Motor-efferent-centrifugal. 11. (See diagram 4) a. Types of autonomic: 1. Sympathetic: Dilator muscle, blood vessels. 2. Parasympathetic: Sphincter, lacrimal, ciliary body. B. Sensory information: 1. General: Almost all sensory information is via the (V) Trigeminal sensory root arising from the trigeminal ganglion. a. The sensory root has dendrites to surface, axons to the CNS. b. Trigeminal ganglion: Gasserian ganglion, contains the cell bodies of three divisions of the V. nerve (ophthalmic, maxillary, mandibular). 2. Branches of (V.) Trigeminal nerve: a. Ophthalmic: 1. Travels through lateral wall of cavernous sinus. 2. Just superior orbital fissure it takes three branches: a. Lacrimal nerve: Above annulus of Zinn, runs along upper border of LR to lacrimal gland, also branches to lateral lid. b. Frontal nerve: Above annulus of Zinn, runs forward above levator and branches into: 1. Supratrochlear nerve: To trochlear area, conjunctiva, medial upper lid, forehead, corrugator, and frontalis. 2. Supraorbital nerve: Parallels supraorbital artery, leaves orbit at SOF, to upper lid, conjunctiva, forehead, frontal muscle. c. Nasociliary nerve: Through Annulus of Zinn, passes below SR and SO to medial orbit. 1. Long or sensory root of ciliary ganglion: Sensory info passes through, no synapse, exits via short ciliary nerves to suprachoroid, sclera, cornea, iris, ciliary body, and choroid. 2. Long ciliary nerves (2): Pierce sclera and run in suprachoroid to cornea, iris, and ciliary body. 3. Anterior ethmoidal nerve: Parallel to anterior ethmoidal artery, through ethmoidal sinus and mucous membrane of nose. 4. Posterior ethmoidal nerve: To ethmoidal and sphenoid sinuses. 5. Infratrochlear nerve: Medial conjunctiva, lids and nose, lacrimal sac, and caruncle. b. Maxillary Division: 1. Travels in lateral wall of cavernous sinus. 2. Exits skull through foramen rotundum, enters orbit through IOF, with two important branches in orbit: a. Infraorbital nerve: 1. Parallels infraorbital artery. 2. Serves lower lid and face. b. Zygomatic: 1. Serves lateral side of orbit and lateral face. c. Mandibular Division: 1. Exits skull through foramen ovale. 2. Serves lower half of face and jaw. C. Visual pathway: 1. Definition: A series of five cells and four synapses, activated during vision (perception of an image in the field of view). a. Photoreceptor cell: Absorbs light energy and converts it to chemical energy. b. Bipolar cell. c. Ganglion cells: Axons transverse nerve fiber layer, optic nerve, chiasm, optic tract, and LGN. d. LGN cells: Axons transverse optic radiations to visual cortex. e. Visual cortex cells: Perception, Broadman area #17. 2. Anatomy of the visual pathway: a. Retina: Not a typical sensory nerve, it is an extension of the CNS. b. Optic nerve: 1. types of fibers: a. Visual pathway fibers: Axons of ganglion cells going to LGN. b. Afferent pupillary fibers: Axons of ganglion cells going to the tectum, pupillary response to light. c. Efferent fibers. 2. Length is 40 to 50 mm. a. Intraorbital: 24 mm. b. Intracanal: 5 mm. (in optic canal). c. Intracranial: 10 mm. (pre-chiasm). 3. Arrangement of fibers in the optic nerve: (See diagram 5) c. Chiasm: 1. Location: a. Anterior wall and floor of third ventricle, surrounded by cerebral spinal fluid. b. Internal carotid artery is lateral. c. Pitutary (hypophysis) is inferior. d. Anterior cerebral and anterior communicating arteries are superior to anterior chiasm. 2. Passage of fibers through chiasm: a. Temporal fibers do not cross over. b. Lower nasal retinal quadrant: Long loops forward (knees of Wilbrand) after crossing. c. Upper nasal retinal quadrant loops posterior before crossing. d. Nasal macular crossover, no loops. e. Temporal macular straight through, no crossover. d. Lateral geniculate nucleus (LGN): 1. Part of thalamus: In thalamus each sensory system has an important system of synaptic connections, LGN for vision which alters information. a. Six cone-like layers of cells: 1. Four upper layers are the Parvocellular layers. a. These are the most inferior layers. 2. Two lower layers are the Magnocellular layers. b. Each layer receives tract fibers from only one eye. 1. Layers 1,4,6, receive from contra eye. 2. Layers 2,3,5, receive from ipsilateral eye. c. Each ganglion cell axon goes only to one layer. d. Within layers they branch five to six times, each synapse with a different LGN cell. e. Lower retina to lateral part, upper retina to medial part, macular retina to posterior part. e. Optic radiations: Axons of LGN cells (geniculo-calcarine pathway). 1. Fibers from medial LGN (upper retina) form upper portions of radiations, go to upper half of visual cortex (cuneus gyrus). 2. Fibers from lateral LGN (lower retina) form lower part of radiations, loops of Meyer, go to lower half of visual cortex (lingual gyrus), (loops of Meyer are from the lower radiations forward into temporal lobe). 3. Fibers from posterior LGN (macular retina) go in middle of radiations to posterior cortex, upper to cuneus gyrus, lower to lingual gyrus. f. Visual cortex: Primary visual cortex, striate cortex, broadman #17, occipital cortex. 1. Location: Inner medial surface, both hemispheres, extends around tip and a little on outer surface. 2. Divided on medial surface by the calcarine fissure: a. Above: Cuneus gyrus, upper retina. b. Below: Lingual gyrus, lower retina. 3. Midway up and down is striae of Gennari, a thick visually distinct band of axons and dendrites in the region of layer four. 4. In layer four: Axons from LGN. 5. Connections: a. To other visual cortex via commissural fissure. 1. Right visual cortex: Left half of visual field. 2. Left visual cortex: Right half of visual field. b. To frontal eye fields, keeps image on fovea. c. With parastria (18) and peristria (19), psychovisual areas associated with memory. d. With superior colliculus. e. With oculomotor nuclei: Descending fibers in optic radiations in occipital mesencephalic tract. g. Field changes: Backwards. 1. Retinal loss: Usually isolated, monocular scotoma, may be binocular if systemic. 2. Severed optic nerve: Blindness, also results from total retinal degradation or opaque cornea, lens, and vitreous. 3. Saggital cut at chiasm: Nasal fibers, bitemporal heteronymous hemianopsia. 4. Pituitary tumor: Pressure on chiasm, bitemporal heteronymous hemianopsia. 5. Aneurism of right internal carotid artery: Pressure on right side of chiasm, loss of left field in right eye, loss of temporal field in both eyes. 6. Sever geniculo calcarine tract: Opposite homonymous hemianopsia. 7. Affect loops of Meyer: Affects lower retina, opposite superior homonymous quadrantanopsia. 8. Damage to posterior cortex: Central field loss.</text>
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<text>XVI. Terms and facts: 1. The cornea is the most powerful refracting surface of the eye. 2. Refractive index of the cornea is = 1.376. 3. Index of refraction of the aqueous is = 1.336. 4. Emmetropia is normal vision. 5. Myopia: Nearsighted, image focus falls in front of the retina, a concave lens (-) is used to correct this condition. 6. Hyperopia: Farsighted, image focus falls behind the retina, a convex lens (+) is used to correct this condition. 7. Presbyopia: Loss of accommodation due to age. 8. Exophthalmos: Protruding eyes. 9. Enophthalmos: Recessed eyes.10. Diffusion: Process by which distribution of molecules happens.11. The retina is an extension of the central nervous system.12. Dialysis: Water is transferred into a solution of protein.13. Ultrafiltration: Salt is transferred into a solution of protein. Dialysis in the presence of hydrostatic pressure. 14. Index of refraction of the lens is = 1.390. </text>
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