Ocular surface

Question 1

What are the 3 layers of the tear film?

Answer 1

Lipid layer, aqueos layer, mucin layer

Question 2

What produces lipid, aqueous and mucin

Answer 2

Lipid –> meibomian glands
Aqueous ==> lacrimal gland
Mucin –> goblet cells

Question 3

What are three parts of the conjunctive?

Answer 3

Palpebral conj,
Bulbar conj.
Forniceal conj.

Question 4

What are the layers of the cornea?

Answer 4

Epithelium 
Bowman's layer
Stroma 
Descemet's membrane 
Endothelium

Question 5

Layers of epithelium of cornea? (3)

Answer 5

Superficial cells 
Middle zone (wing cells) 
Basal cells (stains with periodic acid)

Question 6

What do dermatan sulphate and keratan sulphate do?

Answer 6

Bind to colleagen at specific points to regulate fibril spacing and thickness of interfibrillar space

Question 7

What do dermatan sulphate and keratan sulphate do?

Answer 7

Bind to colleagen at specific points to regulate fibril spacing and thickness of interfibrillar space

Question 8

in corneal endothelium, what cell density causes oedema,swelling ettc

Answer 8

<800 cells/mm2

Question 9

How many cells are required for transplantation

Answer 9

1500/mm2 in a donor is too low for transplantation

Question 10

What is the sensory supply to the cornea?

Answer 10

V1 –> long ciliary nerves –> annular plexus near limbus –> form a subepithelial plexus after losing their myelin sheath –> Intraepithelial plexus

Question 11

Iris divided into 2 via?

Answer 11

collarette

Question 12

Iris sympathetic/parasympathetic supply?

Answer 12

sympatheic –> long ciliary neres

parasympathetic –> short ciliary nerves

Question 13

Type of Collagen found in iris?

Answer 13

Type 1 and 3

Question 14

• Ciliary body dis-insertion from scleral wall is called??

Answer 14

ciliary body cleft

Question 15

• Pilocarpine lowers IOP via?

Answer 15

contraction of longitudinal muscles of ciliary body causes distrention of the inter and intra trabecular spaces of the trabecular meshwork and lowers IOP

Question 16

• Rods to cone ratio?

Answer 16

20:1

Question 17

Most retinal cell nuclei lay in what layer?

Answer 17

OUTER NUCLEAR LAYER

Question 18

• Components of the blood retinal barrier

Answer 18

Outer BRB - tight junctions b/w ONL

Inner BRB - junctions b/w retinal vessel endothelium

Question 19

What are the main collagen types in following tissue?

Sclera ———–
Lens capsule ———–
Vitreous ———–

Answer 19

Sclera ———– 1 and 3
Lens capsule ———– 4
Vitreous ———– 2

Question 20

Where is the thinnest part of sclera? Why is it important?

Answer 20

Behind recti/EOM insertio. Forms a frequent site of scleral rupture following trauma

Question 21

What is the blood supply of rectus muscles? Which one has

only one blood supply?

Answer 21

Anterior ciliary artery

The lateral rectus has one associated anterior ciliary artery

Question 22

Refraction power (dioptre) of
 eye ------
 lens ------
 air-tear +43.6 D
 tear-cornea +5.3 D
 cornea-aqueous -5.8 D

Answer 22

eye —— 58 D

lens —— 15 - 18 D

Question 23

Refractive index of
 lens ------
 vitreous ------
 air 1
 tear 1.336
 aqueous Humor 1.336
 cornea 1.376

Answer 23

lens —— 1.406 (nucleus). 1.36 (cortex)

vitreous —— 1.33

Question 24

Three layers of tear film?

Answer 24

Mucin
Aqueos
lipid

Question 25

What cells in conjunctiva produce mucin?

Answer 25

Goblet cells

Question 26

what is a pterygium?

Answer 26

benign growth of the conjunctiva characterized by elastotic degenration of collagen

Question 27

What are the two processses that contribute to corneal deturgescence?

Answer 27

evaporation of the surface and the corneal epithelial pump

Question 28

What is the normal endothelial cell count of the cornea at birth and at 40 years of age?

Answer 28

Birth : 3000 - 4000 cells / mm2

40 years: 2,500 cells / mm2