Topic 3: Sclera

Question 1

state its functions

Answer 1

(1) protects the internal structures from injury
(2) provides anchorage for structures inside and outside globe
(3) site of attachment (thinnest/weakest part of sclera) to recti muscles - anteriorly, spiral of tillaux
(4) allow retinal blood vessels and nerves to enter the eye by its several openings

Question 2

what is the sclera made up of

Answer 2

75% collagen and proteins, 25% mucopolysaccharides

Question 3

how much does the sclera extend around the eye

Answer 3

anteriorly, it is continuous with cornea (corneoscleral junction - limbus) and exposed to external environment

the rest is surrounded by tenon’s capsule (thin membrane) to separate sclera from orbital fat and fuses with the sclera at the exit of the optic nerve and limbus

Question 4

state layers of sclera

Answer 4

episclera, sclera stroma, lamina fusca

Question 5

describe episclera

Answer 5

anterior most

highly vascularised (vessels from anterior ciliary arteries)

Question 6

describe sclera stroma

Answer 6

consists of LOOSE fine collagen fibres (75%)

the fibres are of variable thickness - increasing strength/toughness of sclera

the fibres are irregularly arranged - makes sclera opaque

avascular

Question 7

describe lamina fusca

Answer 7

innermost

consists of collagen fibres BUT is faintly brown due to melanocytes

separated by choroid by perichorioidal space

Question 8

state its blood and nerve supply

Answer 8

anterior & posterior ciliary arteries, and trigeminal nerve (CNV) respectively