Week 10: Sclera, Conjunctiva & Limbus Flashcards
What is the sclera?
-Posterior 5/6th of globe’s connective tissue coat
-Tough, white, outer layer of eye
-Maintains shape of globe, resists internal/external forces
-Provides the eye with structural strength and protects against penetration and rupture. (Rarely, the sclera becomes inflamed = scleritis)
- The sclera is essentially a continuation of the cornea, as corneal collagen fibres are continuous with those of sclera
- Sclera is perforated by numerous nerves and blood vessels
What is the episclera?
The episclera is thin tissue layer overlying sclera and contains minute blood vessels that supply nutrients to the sclera. (Sometimes episclera becomes inflamed = episcleritis)
What are the three layers of the episclera?
- Outermost layer
- Loose connective tissue (Tenon’s capsule.)
- Rich blood supply (Anterior ciliary vessels)
What is the scleral stroma?
Collagen fibres— Irregularly arranged
Elastic fibres, melanocytes, fibroblasts
What is the anterior sclera? And what is limbus?
Outer coat of the eye, surrounds the cornea at the front of the eye.
-limbus is the transition zone from sclera (white) to cornea (transparent)
What are the cells of the anterior sclera?
Anterior sclera has layer of transparent conjunctival cells covering it (called Bulbar Conjunctiva), as well as part of a connective tissue sheath (called Tenon’s Capsule)
What is Tenon’s capsule?
Tenon’s capsule (TC) is a connective tissue sheath which partly covers anterior sclera. TC starts at limbus and lid muscles, initially fused to conjunctiva, loose matrix, follows sclera round globe, “sleeves” around rectus and oblique muscles, attached to optic nerve sheaths
Sometimes also referred to as ‘anterior fascial sheath’
What are the 2 main layers of sclera?
Episclera: just beneath bulbar
conjunctiva and scleral stroma is deeper lying. Both are ‘fibrous’ layers
Lamina Fusca: lies underneath (inside) sclera, next to choroid
