Uvea (iris, choroid and ciliary body), limbus and sclera


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

Nat Pernick, M.D.
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Table of Contents
Definition / general
Cite this page: Pernick N. Sclera. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/eyeuveasclerageneral.html. Accessed September 26th, 2023.
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
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