Anatomy Of Cornea

Question 1

Volume of the eyeball?

Volume of the orbit?

Answer 1

6ml

30ml

Question 2

Structure in outer layer of eyeball?

Answer 2

Cornea
Sclera
Limbus

Question 3

Structures in middle layer of eyeball

Answer 3

Iris
Ciliary body
Choroid

Question 4

Blood supply of cornea?

Answer 4

Avascular

Question 5

Nerve supply of cornea?

Answer 5

TON-

Trigeminal nerve= Ophthalmic division ka Nasociliary branch

Question 6

Corneal sensation is tested by?/

How to diagnose corneal anaesthesia?

Answer 6

By corneal blink reflex using a cotton wisp

Question 7

Causes of cornea anaesthesia are?

HDL ACTS

Answer 7

H- herpes(99% of times)
D- diabetes
L- leprosy

A- acoustic neuroma
C- contact lens
T- topical timolol ( beta blocker)
S- surgical trauma

Question 8

Affarent pathway for corneal blink reflex?

Efferent pathway ?

Answer 8

Trigeminal branch

7th CN to orbicularis oculi

Question 9

What is lagophthalmos?

Answer 9

Inability to blink the eye.

Seen in Bell’s palsy characterised by orbicularis oculi palsy.

Question 10

Enumerate the layers of cornea?

Answer 10

Outermost Epithelium
Bowman's layer
Stroma
Dua's layer
Descemet's membrane
Innermost endothelium

Question 11

Type of epithelium of cornea?

Answer 11

Non keratinised stratified squamous epithelium.

Corneal epithelium can regenerate d/t basal cells in stratified layer.

Question 12

How will you demonstrate that Bowman’s layer is not a true basement membrane?

Answer 12

It is PAS negative unlike true basement membranes.

Question 13

Can Bowman’s layer regenerate?

Answer 13

Bowman’s layer is acellular. It heals by scar formation.

Question 14

Types of corneal opacity?

Answer 14

Nebular(faint)
Macular
Leukomatous(dense/completely white)

Question 15

Describe macular type of corneal opacity?

Answer 15

In macular, pupillary margin is visible while iris structural details are not visible.

Question 16

Type of corneal opacity which causes max visual disturbance/distortion?

Answer 16

Nebular.

In this, both pupillary margins and iris structural details are visible.

Question 17

Which corneal layer contributes to 90% of corneal thickness?

Answer 17

Stroma.
MC type of collagen in it- Type 1
MC type of glycosaminoglycan- Keratin sulphate

Question 18

Which is the strongest corneal layer?

Answer 18

Dua’s layer

Question 19

Which layer of cornea is secreted continuously by underlying endothelium?

Answer 19

Descemet’s membrane.

It’s thickness inc throughout life, and can regenerate.

Question 20

What is schwalbe’s line?

Answer 20

Peripheral termination of descemet’s membrane.

Question 21

How does corneal endothelium help to maintain corneal transparency?

Answer 21

@ Has active Na-K ATPase to maintain corneal dehydration (cornea becomes hazy if becomes edematous)
@ Has tight junctions between adjacent endothelial cells

Question 22

Normal endothelial cell count?

Answer 22

2400-3000 cells/mm3

Question 23

How does corneal endothelium adapt of endothelial cell count is <2400 but >500?

Answer 23

By polymegathism(enlargement of normal cells)
And by polymorphism ( cells change their shape to adapt and maintain corneal transparency)

Question 24

Investigation done for endothelial cell count?

Answer 24

Specular microscopy

Question 25

Factors that maintain corneal transparency are?

Answer 25

@tear film( keeps surface moist and helps light travel in straight line)
@avascularity of cornea
@collagen fibres in stroma- uniform in diameter with equal distance between all collagen fibrils
@corneal dehydration maintained by endothelium
@Normal intra-ocular pressure
@crystallins in corneal stroma reduce the backscatter of light

Question 26

Surface ectoderm derivatives of eye?

Answer 26

TELL

Tarsal plate, Ep of cornea and conjunctiva, lacrimal gland, lens