Applied Anatomy and Physiology of The Eye

Question 1

What type of epithelium is the cornea?

Answer 1

Stratified squamous non-keratinised epithelium

Question 2

What are the layers of the cornea?

Answer 2

Epithelium
Bowman’s membrane - basement membrane of corneal epithelium
Stroma
Descemet’s layer - thick basement membrane
Endothelium - single layer

Question 3

Describe the stroma of the cornea

Answer 3

Regularly arranged collagen
No blood vessels

Question 4

What is the tool used for microscope of eye?

Answer 4

Slit lamp - thin beam of rays

Question 5

How is transparency of the cornea maintained?

Answer 5

Regular arrangement of collagen in stroma
No blood vessels
Endothelium cell layer has pump which actively keeps AH out

Question 6

What happens if there is caps in endothelium cells of cornea?

Answer 6

AH can push in causing opacification

Question 7

What causes corneal opacities?

Answer 7

Healing of wounds of cornea leads to loss of transparency

Question 8

How does avascularity play an important role in corneal transplant?

Answer 8

Is benefit when performing graft surgery as lesser chance of foreign antigens from corneal graft being recognised by recipient - lesser chance of graft rejection
Cornea is immune privileged site

Question 9

How is the angle of anterior chamber seen on slit lamp?

Answer 9

Needs lens in front of cornea to eliminate refraction from cornea
Gonioscope
Light rays from angle of anterior chamber come onto 3 mirrors and reflect

Question 10

Describe degeneration of the trabecular meshwork

Answer 10

No longer able to drain AH
This increases intraocular pressure - glaucoma
If left untreated pressure will end up affecting optic nerve cells on retina and killing them leading to blindness

Question 11

What is the choroid made up of?

Answer 11

Fenestrated blood vessels of varying diameter
Supply outer layers of retina with blood by diffusion
Inner layer of retina get blood from branches of central retinal artery

Question 12

How many layers of the retina?

Answer 12

10
9th layer is the nerve cell layer
2nd layer is the layer of rods and cones - contains photo active neurons
And 3rd layer is outer limiting membrane

Question 13

Describe the fovea centralis

Answer 13

Central part of retina with maximum visual acuity
Packed with cones and layers used to side

Question 14

What is lens opacification called and how does it happen?

Answer 14

Cataract
Is transparent as avascular
Avascularity predisposes to becoming opaque later in life

Question 15

What are the functions of tear film?

Answer 15

Keeps cornea moist and prevents drying
Washes away any particular foreign bodies
Has antibodies and lysosomes to kill microbes
Smooth outer surface of cornea providing smooth surface of retraction

Question 16

What dye can you use clinically to see tear film?

Answer 16

Fluorescein

Question 17

Describe the structure of the tear film

Answer 17

3 layers
1 - mucinous layer overlying corneal epithelium
2 - aqueous layer
3 - oily layer is most superior and delays evaporation

Question 18

Describe the tear film dynamics

Answer 18

During a blink, sharp lower border of upper eyelid distributes tear film
When eyelids open, aqueous layer begins to evaporate and oily layer comes close to mucus layer
When these layers touch, film breaks up so further blinking