-- card: 7237 from stack: in
-- bmap block id: 7607
-- flags: 0000
-- background id: 2278
-- name: Vitreous


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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.