-- card: 6163 from stack: in -- bmap block id: 6461 -- flags: 0000 -- background id: 2278 -- name: Uveal Tract -- part 1 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=261 top=324 right=336 bottom=273 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 14000 end mouseUp -- part 2 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=276 top=324 right=336 bottom=288 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 14206 end mouseUp -- part 3 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=291 top=324 right=336 bottom=303 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 14533 end mouseUp -- part 4 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=306 top=324 right=336 bottom=318 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 14632 end mouseUp -- part 5 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=321 top=324 right=336 bottom=333 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 15074 end mouseUp -- part 6 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=336 top=324 right=336 bottom=348 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 15262 end mouseUp -- part 7 (button) -- low flags: 00 -- high flags: 2000 -- rect: left=351 top=324 right=336 bottom=363 -- title width / last selected line: 0 -- icon id / first selected line: 0 / 0 -- text alignment: 1 -- font id: 0 -- text size: 12 -- style flags: 0 -- line height: 16 -- part name: 1 ----- HyperTalk script ----- on mouseUp visual iris close go to card id 15378 end mouseUp -- part contents for background part 1 ----- 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.