Term
| Which cells of the corneal epithelium contain Keratin 3? |
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Definition
| only the wing cells; this is how you tell them apart from the basal cells |
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Term
| What effect does vitamin A deficiency have on the cornea? |
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Definition
| It makes the nonkeratinized cornea express the cornified cytoskeletal elements typical of the keratinized cornea. |
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Term
| At what stage does the process of apoptosis begin in the cornea? |
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Definition
begins as the basal cell turns into a wing cell |
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Term
| Which cells are more likely to be sloughed off, smaller and lighter or darker and larger? |
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Definition
| the darker and larger cells |
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Term
| What is the significance of the collagen fibrils of the cornea turning and running parallel at the limbus? |
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Definition
This effects corneal curvature |
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Term
| What is the function of the corneal stromal keratocytes? |
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Definition
1. produce collagen and proteoglycans
2. maintain and repair matrix organization
Keratocytes are the fibroblasts of the cornea. Fibroblasts are connective tissue cells with cytoplasmic processes (support and bind fibrous) tissue throughout the body |
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Term
| What are the shepherds of the fibril? |
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Definition
| keratocytes because they keep the fibrils in parallel to induce corneal transparency |
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Term
| What is the function of Bowman's layer? |
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Definition
| Probably protective. It has a decreased amount of type 1 collagen |
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Term
| What do 50% of RCEs (recurrent corneal erosions) start from? |
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Definition
| EBMD (Epithelial Basement Membrane Disease) |
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Term
| What disease has the characteristics of fibrillar material between the BM and Bowman's and intraepithelial microcysts formed by trapped degenerating epithelial cells It has a thickened BM with fingerlike lamella stretching into the overlying epithel |
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Definition
| EBMD (epithelial basement membrane disease) |
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Term
| What disorder causes and abnormal KS synthesis causing closer spaced fibrils? |
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Definition
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Term
| What proteoglycan disorder produces aggregates in the corneal stroma due to a metabolic disorder? |
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Definition
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Term
| What is the purpose of Bowman's membrane? How is it effected during keratoconus? |
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Definition
| Bowman's membrane provides structure to the cornea. If it thins, the cornea may bow at the center and result in keratoconus. |
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Term
| What layer of Descemet's membrane increases with age? |
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Definition
The posterior banded layer which is closest to the endothelium |
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Term
| What are four characteristics of posterior polymorphous dystrophy in the endothelium? |
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Definition
Posterior laminar banding in Descemet's membrane
In this disorder, the endothelium also takes on epithelial like characteristics.
1. Microvilli
2. multilayered
3. keratin filaments increase
4. desmosomes increase
None of these four are characteristic of normal corneal endothelium. |
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Term
In which disorder does the endothelium secrete abnormal Descemet's collagenous excretion? It occurs in 10% of normal eyes over 50. |
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Definition
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Term
| Which eye disease results from corneal endothelial thinning (hence decreased endothelial pumping) and a swollen thickened cornea? It's associated with microcyst formation. |
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Definition
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Term
| Which disease is characteristic of an intact Descemet's membrane after a corneal or stromal ulceration that protrudes forward like a blister? It is because Descemet's membrane is resistant to rupture. |
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Definition
| Descemetocele-anything "cele" means a bulging |
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Term
| What are some common causes of rupture of Descemet's membrane? |
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Definition
1) contusions
2) forceps delivery at birth
3) buphthalmos-infantile glaucoma
4) surgical insult |
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Term
| Can young people lay down additional Descemet's membrane to cover up a rupture? |
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Definition
| Yes, but it's difficult for older people. |
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Term
| What cytokine prevents sterile ulceration by inhibiting Type I collagenase activity by stromal keratocytes? |
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Definition
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Term
| What is the purpose of type I collagenase activity in corneal wound repair? |
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Definition
| It cleans up the damaged area by breaking down the collagen. It's present within 9 hours of the wound but it peaks out after 14-21 days after the injury. |
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Term
| What enzyme degrades the basement membrane during corneal wound healing? |
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Definition
| MMP-9 (Matrix metalloproteinase) |
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Term
| What effect does sympathetic dennervation have on corneal wound healing? |
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Definition
| It increases migration but it decreases mitosis |
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Term
| What effect does overstimulation of the sympathetic nerves have on corneal wound healing? |
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Definition
It may impair healing by decreasing migration |
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Term
| When would it be beneficial to give a patient with a corneal stromal injury a steroid to reduce scarring? |
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Definition
| within the first 7-10 days, after that you're not reducing inflammation as much as you're suppressing cell migration and wound healing |
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