Cornea

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Overview


The cornea is a transparent structure situated at the front of the eye. It is also commonly known as the “clear window of the eye”. It has two main purposes, which are protecting the eye from injury and infection and focusing light into the eye. It has more light focusing power than the lens. It is made up of five different layers.

This image demonstrates the cornea, which is a clear transparent layer that is located in front of the iris (a structure that gives the eye colour) and the lens.
Location of the cornea in relation to the iris and lens as seen normally (A) and a three dimensional illustration (B). Note the cornea (in green circle) is in front of the iris and the lens
The five layers of the cornea are outlined here, with the epithelium being the most superficial layer, followed by Bowman's layer, stroma (thickest layer), Descemet's membrane and endothelium.
Layers of the cornea


Layers of the cornea


  • Epithelium
This is the most superficial layer of the cornea. The cells here provide an optimal surface to keep the cornea moist and clear. These cells are constantly shed and replaced by stem cells located in the limbus. An imbalance in this process causes the eye to be chronically dry and irritable, leading to discomfort and visual deterioration.
This image demonstrates the location of the limbus. It appears as the junction between the coloured part of the eye and the white of the eye.
Location of the limbus in relation to the cornea and conjunctiva
  • Bowman’s layer
This is a dense connective tissue layer separating the epithelium and stroma.
  • Stroma
This is the thickest layer of the cornea. It provides structural toughness to the cornea and the special arrangement of the cells here gives rise to its transparency.
  • Descemet’s membrane
This is a dense connective tissue layer separating the stroma and the endothelium.
  • Endothelium
This is the innermost layer. Cells here regulate the fluid content in the cornea. Damaged or diseased cells causes swelling of the cornea, disrupting its transparency and therefore affects vision.