Eye
Uvea (iris, choroid and ciliary body), limbus and sclera
Sclera
Author: Nat Pernick, M.D.
Last author update: 1 February 2014
Last staff update: 29 December 2020
Copyright: 2004-2024, PathologyOutlines.com, Inc.
PubMed Search: Sclera [title] eye review[ptyp]
Table of Contents
Definition / generalCite this page: Pernick N. Sclera. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/eyeuveasclerageneral.html. Accessed April 19th, 2024.
Definition / general
- 80% of surface area of eye
- Begins at periphery of cornea, extends posteriorly to optic nerve
- Relatively rigid; protects eye from trauma and maintains intraocular pressure
- Visible anteriorly under transparent conjunctiva; white in adults
- Thickness varies; 0.3 mm at insertion of rectus muscles, 0.8 mm at limbus and 1.0 mm at insertion of optic nerve
- Weakly attached to underlying choroid by thin collagen fibers
- Heals poorly due to few blood vessels or fibroblasts
- Aging related changes include calcification between collagen fibers, senile scleral plaques
- Composed of episclera, stroma and lamina fusca
- Episclera: most superficial part of sclera, located between fibrous structure that envelopes the globe (Tenon capsule) and scleral stroma; composed of loose collagen fibers and fibroblasts with numerous vessels, occasional melanocytes and mononuclear white blood cells
- Stroma: largest component of sclera, randomly arranged bands of collagen with occasional elastic fibers and fibroblasts; minimal blood vessels except in perforating emissiary canals, accompanied by nerves and scattered melanocytes; rarely contains a prominent nerve (nerve loop of Axenfeld) in an emissiarial canal near limbus, which may mimic a neurofibroma; anterior ciliary arteries perforate sclera near insertion of rectus muscles, posterior ciliary arteries pass through sclera near optic nerve; vortex veins exit sclera posterior to equator of eye
- Lamina fusca: innermost layer of sclera with loose collagen fibers, fibroblasts and scattered melanocytes
