Vitreous Humor.pdf

Vitreous Humor Karen Gil MD, MHSN Vitreous Chamber Filled with gel-like vitreous body The vitreous makes up 80% of the entire volume of the eye Volume: 4ml (size eye 5ml) Spherical shape except the center of the anterior surface contains the patellar fossa (indentation where the lens sits) Vitreous...

Vitreous Humor Karen Gil MD, MHSN Vitreous Chamber Filled with gel-like vitreous body The vitreous makes up 80% of the entire volume of the eye Volume: 4ml (size eye 5ml) Spherical shape except the center of the anterior surface contains the patellar fossa (indentation where the lens sits) Vitreous Chamber Components of the Vitreous: 98.5% to 99.7% water with Collagen Type II collagen fibers GAG substance Hyaluronic Acid Consistency of the vitreous Hyalocites Hyalocites Vitreous cells Located at the cortex near the vitreal surface Vitamin C Higher than plasma Amino Acids Lower than plasma Early life – gel like (jelly) Fig. 3. Schematic diagram of adult vitreous ultrastructure depicting the relationship between hyaluronic acid molecules and collagen fibrils. (Sebag J, Balazx EA: Morphology and ultrastructure of human vitreous fibers. Invest Ophthalmol Vis Sci 1989;30:1871) Vitreous Chamber Human vitreous structure during childhood. This view of the central vitreous from an 11-year-old child demonstrates a dense vitreous cortex with hyalocytes. The posterior aspect of the lens is seen below, though dimly illuminated. No fibers are present in the vitreous. Adler’s Eye Physiology Ultrastructure of human vitreous cortex. Scanning electron microscopy demonstrates the dense packing of collagen fibrils in the vitreous cortex. To some extent this arrangement is exaggerated by the dehydration that occurs during specimen preparation for scanning electron microscopy (magnification = ×3750). Adler’s Eye Physiology Vitreous Changes Age 70-80 – becomes more liquid (center) Pockets of fluid Aggregation of collagen fibrils - floaters Vitreous Attachments 5 attachments to the retina and lens Vitreous base Strongest Most extensive Extends 1.5 to 2mm anterior to the ora serrata Posterior lens Optic disc Macula Annular ring Retinal vessels Fine strands that extend through the internal limiting membrane to branch and surround the larger retinal vessels Tightest attachments have the highest likelihood of causing a retinal tear Vitreous Attachments Vitreous Regions Anterior Hyaloid Weiger’s ligament or retrolental ligament Ring shape tight attach at the posterior lens capsule Berger’s Space space between the ligament and the lens Vitreous Regions Vitreous Cortex Outer region Collagen fibrils, cells, proteins and mucopolysacharides Anterior Vitreous Cortex Hyaloid surface (hyalocites) Extends to the ora serrata Posterior Vitreous Cortex Contain transvitreal channels that appear as holes Peripapillary hole Premacular hole Prevascular fissures Vitreous Regions Intermediate zone Fine fibers that are continuous and unbranched Run antero-posteiorly Cloquet’s Canal Also called hyaloid channel Normal remnant of primary vitreous (at the center) S shape Represents the site of former embryological hyaloid artery Terminates at the area of Martegiani Funnel-shaped space at the optic nerve head Function of the Vitreous Transparent medium of the passage of light 1.33 refractive index Acts as a UV filter (decreases transmission of light at 300-350nm) Acts as a cushion to the globe (especially retina and lens) Absorbs vibrations and external forces during trauma and eye movements Storage are of nutrients for the retina and lens Clinical Applications Vitreous Hemorrhage Neovascularization – Proliferative diabetic retinopathy – Central retinal vein occlusion Rupture of normal vessels – Retinal tear – Trauma – Posterior vitreous detachment – Retinal detachment Vitreous Detachment Trauma Posterior vitreous detachment Weiss ring – usually results from normal, age-related changes in the vitreous gel Clinical Applications Vitreous Asteroid Hyalosis – – – – – Elderly Unilateral Appearance spherical white Moves with vitreous Calcium Synchysis Scintillants – – – – – Young Bilateral Extremely rare Highly retractile multicolored Moves freely and falls to floor of vitreous – Cholesterol crystals