Cornea Vol. 2 Flashcards Preview

Complete Review Course > Cornea Vol. 2 > Flashcards

Flashcards in Cornea Vol. 2 Deck (29):
1

What is the refractive index of the cornea?

1.376

2

What is the average radius curvature of the central cornea?

7.8 mm

3

What is the average power of the cornea in diopters?

43 D

4

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

59 D

5

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

Cornea

6

What type of epithelium composes the corneal epithelium?

Stratified squamous epithelium

7

How thick is the corneal epithelium?

0.05 mm

8

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

Approx. 5%

9

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

Tight junctions

10

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

Type IV collagen

11

What types of collagen are found in the corneal stroma?

Types I, V, and VI

12

What are two major proteoglycans found in the corneal stroma?

Decorin and lumican

13

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

Decreases from anterior to posterior

14

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

78%

15

What creates the swelling pressure of the corneal stroma?

Negatively charged proteoglycans proteoglycans that repel each other

16

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

Anterior stroma

17

How thick is Descemet's membrane at birth?

3 um

18

How thick Is Deseret's membrane In the adult?

10 to 12 um

19

How do radial incisions change the shape of the cornea?

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

20

How do tangential incisions change the shape of the cornea?

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

21

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

Hydration of the corneal stroma

22

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

Hyperopic shift

23

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

Hyperopic shift in the morning

24

What optical characteristic of the cornea makes sclerotic scatter possible?

Total internal reflection

25

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

Fluorescein

26

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

Rose bengal

27

What is an Axenfeld loop?

lntrascleral loop of long posterior ciliary nerve

28

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

Rose bengal

29

What condition is characterized by lower conjunctival staining?

Meibomian gland dysfunction