Cornea Vol. 2

Question 1

What is the refractive index of the cornea?

Answer 1

1.376

Question 2

What is the average radius curvature of the central cornea?

Answer 2

7.8 mm

Question 3

What is the average power of the cornea in diopters?

Answer 3

43 D

Question 4

What is the average total power of the human eye in diopters?

Answer 4

59 D

Question 5

What is the major source of astigmatism in the optical system?

Answer 5

Cornea

Question 6

What type of epithelium composes the corneal epithelium?

Answer 6

Stratified squamous epithelium

Question 7

How thick is the corneal epithelium?

Answer 7

0.05 mm

Question 8

What percentage of the total corneal thickness does the corneal epithelium constitute?

Answer 8

Approx. 5%

Question 9

What structures of the corneal epithelium prevent penetration of the tear fluid into the stroma.?

Answer 9

Tight junctions

Question 10

What type of collagen makes up the basement membrane of the corneal epithelium?

Answer 10

Type IV collagen

Question 11

What types of collagen are found in the corneal stroma?

Answer 11

Types I, V, and VI

Question 12

What are two major proteoglycans found in the corneal stroma?

Answer 12

Decorin and lumican

Question 13

How does the refractive index of the cornea change from anterior to posterior?

Answer 13

Decreases from anterior to posterior

Question 14

What is the normal percentage of water content of the corneal stroma?

Answer 14

78%

Question 15

What creates the swelling pressure of the corneal stroma?

Answer 15

Negatively charged proteoglycans proteoglycans that repel each other

Question 16

Where is the density of keratocytes in the corneal stroma the highest?

Answer 16

Anterior stroma

Question 17

How thick is Descemet’s membrane at birth?

Answer 17

3 um

Question 18

How thick Is Deseret’s membrane In the adult?

Answer 18

10 to 12 um

Question 19

How do radial incisions change the shape of the cornea?

Answer 19

Radial incisions cause flattening in the meridian of the incision and flattening 90 degrees away

Question 20

How do tangential incisions change the shape of the cornea?

Answer 20

Tangential incisions cause flattening of the meridian of the incision and steepening 90 degrees away

Question 21

What factor does the effect of incisional surgery greatly depend on?

Answer 21

Hydration of the corneal stroma

Question 22

What can occur to the refractive error of a patient exposed to high altitude or low P02?

Answer 22

Hyperopic shift

Question 23

What type of diurnal shift can occur in patient following radial keratotomy due to stromal swelling?

Answer 23

Hyperopic shift in the morning

Question 24

What optical characteristic of the cornea makes sclerotic scatter possible?

Answer 24

Total internal reflection

Question 25

What stain is used to detect disruption of intercellular junctions of the cornea?

Answer 25

Fluorescein

Question 26

When compared to fluorescein, what corneal stain is more toxic and more likely to induce reflex tearing?

Answer 26

Rose bengal

Question 27

What is an Axenfeld loop?

Answer 27

lntrascleral loop of long posterior ciliary nerve

Question 28

What corneal stain is a photosensitizer and also has antiviral properties?

Answer 28

Rose bengal

Question 29

What condition is characterized by lower conjunctival staining?

Answer 29

Meibomian gland dysfunction