Eye
Uvea
Sclera - general

Author: Nat Pernick, M.D. (see Authors page)

Revised: 23 May 2018, last major update February 2014

Copyright: (c) 2004-2018, PathologyOutlines.com, Inc.

PubMed Search: Sclera [title] eye review[ptyp]

Table of Contents
Definition / general
Cite this page: Pernick, N. Uvea: sclera - general. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/eyeuveasclerageneral.html. Accessed December 17th, 2018.
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