MCPHS Anterior Seg Cornea Exam Questions And
Accurate Answers
Corneal Innervation
Derived from ciliary nerves that penetrate cornea in deep peripheral stroma, lose
myelination shortly after entering cornea. Terminate in wing cells of epi
Cornea: Epithelium
surface layer, 55um, barrier function (block debris, bacteria, foreign), constantly
regenerated + sloughed
Cornea: Bowman's Layer
Basement membrane, 5um, prevents forward corneal swelling
Cornea: Stroma
Majority of the cornea, 485um, strength + elasticity
Cornea: Dua's Layer
Newly discovered, 10-15um, Unknown fxn
Cornea: Descemet's Layer
basement membrane, 10um, health of endothelial cell
Cornea: Endothelium
Innermost layer, 5um = 1 cell thick, barrier pump maintaining appropriate corneal
hydration
, Arcus Senilis
Degenerative change involving deposition of lipid in peripheral cornea. Gray/white arc
progresses into a ring with sharp peripheral border and diffused central border. Limbal
intervening zone.
Fish-Eye Disease
LCAT deficiency -- progressive arcus which begins in adolescence. May result in
complete opacification. Usually asymptomatic besides cosmesis.
Lipid Degeneration
Dense yellow-white opacity that may fan out with feathery edges. Deposits consist of
cholesterol, fats, phospholipids. Two types: (primary + secondary)
Spheroidal Degeneration
Clear to yellow-gold spherules seen in subepithelium, within Bowmans, or in superficial
corneal stroma. They may darken with age. Three types: (primary corneal involvement,
corneal involvement 2^ to underlying, conj involvement)
Amyloid Degneration
Groups of proteins with starch-like characteristics. Stains with Congo Red, birefingence
in polarized light, and dichromism in green light. Primary of secondary forms
Salzmann's Nodular Degeneration
Yellow-white to blue elevated lesions on cornea. Usually annular pattern in
mid-periphery. Adjacent to corneal scars or pannus. F>>M.
Terrien's Marginal Degeneration
Non-inflammatory peripheral thinning with pannus. White/grey band 1-2mm that starts
superonasally and spreads circumferentially. A gutter forms between opacity and
limbus (depression)
Accurate Answers
Corneal Innervation
Derived from ciliary nerves that penetrate cornea in deep peripheral stroma, lose
myelination shortly after entering cornea. Terminate in wing cells of epi
Cornea: Epithelium
surface layer, 55um, barrier function (block debris, bacteria, foreign), constantly
regenerated + sloughed
Cornea: Bowman's Layer
Basement membrane, 5um, prevents forward corneal swelling
Cornea: Stroma
Majority of the cornea, 485um, strength + elasticity
Cornea: Dua's Layer
Newly discovered, 10-15um, Unknown fxn
Cornea: Descemet's Layer
basement membrane, 10um, health of endothelial cell
Cornea: Endothelium
Innermost layer, 5um = 1 cell thick, barrier pump maintaining appropriate corneal
hydration
, Arcus Senilis
Degenerative change involving deposition of lipid in peripheral cornea. Gray/white arc
progresses into a ring with sharp peripheral border and diffused central border. Limbal
intervening zone.
Fish-Eye Disease
LCAT deficiency -- progressive arcus which begins in adolescence. May result in
complete opacification. Usually asymptomatic besides cosmesis.
Lipid Degeneration
Dense yellow-white opacity that may fan out with feathery edges. Deposits consist of
cholesterol, fats, phospholipids. Two types: (primary + secondary)
Spheroidal Degeneration
Clear to yellow-gold spherules seen in subepithelium, within Bowmans, or in superficial
corneal stroma. They may darken with age. Three types: (primary corneal involvement,
corneal involvement 2^ to underlying, conj involvement)
Amyloid Degneration
Groups of proteins with starch-like characteristics. Stains with Congo Red, birefingence
in polarized light, and dichromism in green light. Primary of secondary forms
Salzmann's Nodular Degeneration
Yellow-white to blue elevated lesions on cornea. Usually annular pattern in
mid-periphery. Adjacent to corneal scars or pannus. F>>M.
Terrien's Marginal Degeneration
Non-inflammatory peripheral thinning with pannus. White/grey band 1-2mm that starts
superonasally and spreads circumferentially. A gutter forms between opacity and
limbus (depression)
