Eye
General
Anatomy & histology-cornea
Author: Nat Pernick, M.D.
Last author update: 1 October 2013
Last staff update: 5 March 2021
Copyright: 2004-2023, PathologyOutlines.com, Inc.
PubMed Search: Cornea [title] anatomy [title] and histology
Table of Contents
Definition / general | Vasculature | Hasall-Henle bodies (warts) | Myopia | Hyperopia | Laser assisted in situ keratomileusis (LASIK) | Microscopic (histologic) images | Drawings | Positive stains | Negative stains | Additional referencesCite this page: Pernick N. Anatomy & histology-cornea. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/eyecorneaanatomy.html. Accessed September 26th, 2023.
Definition / general
- Wider than tall (11.7 mm horizontally vs. 10.6 mm vertically)
- Thickness varies from 0.5 mm (central) to 0.67 mm (peripheral)
- Cornea and overlying tear film are major refractive surface of eye, not the lens
- 6 distinct layers (outside to inside):
- Outer epithelium: stratified squamous, nonkeratinized, 5 layers thick centrally, thicker peripherally, polygonal at basal layer but flatten as they approach surface; basal cells may have mitotic figures; Langerhans cells are CD1a+; note: layers often “rubbed off” while grossing specimen
- Epithelial basal lamina (basement membrane): highlighted with PAS stain
- Bowman layer: most anterior stroma, acellular, 8 - 14 microns thick, not a true basement membrane, composed of randomly oriented delicate collagen fibers, does not regenerate
- Stroma: also called substantia propria, no blood vessels or lymphatics, 90% of cornea's thickness, contains regularly spaced collagen fibrils; normally separated by glycoprotein and mucoprotein which makes cornea transparent; normally see stromal lamellae separated by clefts, a processing artifact, absence of clefts is caused by stroma edema (causes corneal "clouding"), due to damage of "endothelium"
- Descemet [pronounced DEZMET] membrane: a true basal lamina produced by underlying corneal endothelial cells; 3 - 4 microns at birth, 10 - 12 microns in adults; does not regenerate; site of copper deposition in Kayser-Fleisher ring of Wilson disease
- "Endothelium": single layer of very flat cells, does not regenerate, functions as pump to keeps cornea dehydrated and transparent
- Neural crest origin (S100+); does NOT line blood vessels or lymphatic spaces; directly contacts aqueous humor of anterior chamber, often “rubbed off” while grossing specimen
Vasculature
- No blood vessels or lymphatics within cornea
- Arterial plexus is present at junction of cornea and sclera
- Is also nourished by aqueous humor of anterior chamber
Hasall-Henle bodies (warts)
- Focal excrescences that form on peripheral Descemet membrane with normal aging
- Not seen in surgically excised corneal buttons because are too peripheral in location
Myopia
- Eye too long for its refractive power
Hyperopia
- Eye too short for its refractive power
Laser assisted in situ keratomileusis (LASIK)
- Sculpt cornea and change its refractive properties to eliminate need for glasses
Microscopic (histologic) images
Images hosted on other servers:
Full thickness
Epithelium and Bowman layer
Drawings
Images hosted on other servers:
Cornea
Positive stains
Negative stains
Additional references
