Cornea Vol. 3

Question 1

Histologically, what are conjunctival follicles?

Answer 1

Clusters of lymphocytes

Question 2

What type of cells form “mutton-fat” KP?

Answer 2

Macrophages

Question 3

Where are clusters of follicles located In benign lymphoid folliculosis?

Answer 3

lnferotemporal palpebral and forniceal conjunctiva

Question 4

Where is the thinnest portion of the cornea typically located?

Answer 4

1.50 mm temporal to the geographic center

Question 5

What central corneal thickness increases the risk of symptomatic corneal edema following intraocular surgery?

Answer 5

Greater than 650 um

Question 6

What are Waite-Beet ham lines?

Answer 6

Faint, deep stromal wrinkles seen in early corneal edema

Question 7

What is the average endothelial cell count in children?

Answer 7

3500 cells/mm2

Question 8

What forms keratic precipitates (KP)?

Answer 8

Clumps of Inflammatory cells from the anterior uvea

Question 9

What is the average endothelial cell count In adults?

Answer 9

2400 cells/mm2

Question 10

What is the average endothelial cell size in adults?

Answer 10

150 to 350 um2

Question 11

How is corneal endothelium coefficient of variation calculated?

Answer 11

Mean cell area divided by standard deviation of the cell area

Question 12

What is the normal coefficient of variation of the cornea?

Answer 12

Less than 0.3

Question 13

What is polymegethism?

Answer 13

Increased variation In individual cell areas of the cornea

Question 14

What is the most common cause of increased polymegathism of the cornea?

Answer 14

Contacts lens use

Question 15

Where does corneal neovascularization typically originate in the limbal vascular arcades?

Answer 15

Palisades of Vogt

Question 16

When are Descemet’s folds typically first seen?

Answer 16

When corneal thickness increases by 10% or more

Question 17

What is the average refractive power of the cornea?

Answer 17

43 D

Question 18

What is the refractive power of the air-stroma Interface?

Answer 18

49 D

Question 19

What is the refractive power of the endothelium? aqueous interface?

Answer 19

6 D

Question 20

When does corneal epithelium edema occur?

Answer 20

When corneal thickness exceeds 0.70 mm

Question 21

What is the average endothelial cell count In elderly patients?

Answer 21

2000 cells/mm2

Question 22

How many diopters is the central cornea typically steeper than the periphery?

Answer 22

Approx. 3D

Question 23

What part of the cornea is the area of greatest flattening and asphericity?

Answer 23

Peripheral or “transitional” zone

Question 24

What is Snell’s law?

Answer 24

Refractive power equals difference between two refractive indices divided by the radius of curvature