sclera Flashcards
(16 cards)
What are the primary functions of the sclera?
Maintains the shape of the eyeball
Protects intraocular components
What is the typical colour of the sclera in different age groups?
Bluish in very young (due to the choroid pigment showing through)
Yellowish in elderly (due to lipid deposits)
How does the thickness of the sclera vary across different regions?
Limbus: About 0.5 mm
Muscle insertions: About 0.3 mm
Equator: About 0.4 mm
Posteriorly: About 1.0–1.4 mm
What is Tenon’s capsule and what is its function?
A thin membrane that supports and positions the eyeball
Allows the eyeball to move
Covers the sclera anteriorly and is attached to connective tissue posteriorly
What are the aqueous drainage channels in the sclera?
Canal of Schlemm: Drains aqueous from the anterior chamber
Collector channels: Drain aqueous from Canal of Schlemm
What is the blood supply of the sclera?
Anterior ciliary arteries: Supply recti, sclera, conjunctiva, ciliary body
Vorticose veins: Drain blood from the choroid
Short and long ciliary arteries: Supply choroid, sclera, ciliary body
What are the penetrations found in the sclera?
Lamina cribrosa: Weakest part of the sclera, allows passage of the optic nerve and central retinal artery/vein
Fenestrations in the sclera permit the passage of the optic nerve and retinal vessels
What are the main layers of the sclera?
A:
Episclera: Outermost, vascular layer
Stroma: Dense, irregular connective tissue
Lamina Fusca: Inner layer containing melanocytes
Endothelium: Innermost layer, weakly attached to the choroid
What are the blood vessels that supply the sclera?
Supplied by anterior ciliary arteries, short posterior ciliary arteries, and long posterior ciliary arteries
Venous drainage through episcleral, intrascleral, and deep scleral plexuses into anterior ciliary veins
What is the nerve supply to the sclera?
A:
Sensory innervation from the ophthalmic branch of the trigeminal nerve (CN V) and ciliary nerves (long and short)
Clinical note: Scleritis is very painful, while episcleritis is uncomfortable but not as painful
What are the clinical signs of episcleritis?
Common and benign
Swelling (oedema) in Tenon’s capsule and episclera
Redness from conjunctival and superficial episcleral vessels (brick red appearance)
Redness moves over the sclera
What are the clinical signs of scleritis?
Less common but sight-threatening
Swelling of the entire stroma
Redness from deep episcleral vessels (blueish-red appearance)
Swelling does not move over the sclera
Painful compared to episcleritis
What are the causes and clinical signs of scleral discolouration?
Focal yellow: Age-related scleral translucency
Yellow: May indicate jaundice (bilirubin buildup in conjunctiva)
Blue: May indicate collagen diseases or scleral thinning, which shows underlying choroid
What is the lamina cribrosa and why is it important?
The weakest area of the sclera
Allows the passage of the optic nerve and central retinal artery and vein
Plays a role in increased cupping in glaucoma
Why is it important to recognize episcleritis and scleritis during an optometric examination?
Episcleritis is a benign, uncomfortable condition, while scleritis is more serious and sight-threatening
Early detection is crucial, as scleritis can lead to vision loss if not treated properly
What is the clinical significance of scleral thinning in relation to blue sclera?
Blue sclera may indicate collagen disorders or conditions that lead to scleral thinning
The thinning of the sclera makes the underlying choroid visible, giving the sclera a bluish appearance
