The Cornea

The cornea is a clear, transparent structure, with a brilliant, shiny surface.

It has a convex surface that acts as a powerful lens. Most of the refraction of the eye takes place not through the crystalline lens of the eye but through the cornea.

The cornea is relatively large at birth and almost attains its adult size during the first and second years. Although the eyeball as a whole increases a little less than three times in volume from birth to maturity, the corneal segment plays a small role part in this, being fully developed by 2 years of age.

The cornea is thicker at its periphery (1mm) than at the centre (0.6mm). It can be divided into five distinct portions.

(Fig. 5)

The epithelium. Bowman's membrane, the stroma. Descemet's membrane, and the endothelium.

The epithelium, which is the part of the cornea usually injured with superficial abrasions or small foreign bodies, regenerates rapidly and heals without leaving a scar. Injury to the deeper structures nearly always results in formation of an opacity in the cornea. The cornea contains no blood vessels, as it is completely nourished by a plexus of fine capillaries surrounding it. The junction of the cornea and sclera is demarcated by a gray, semi-transparent area referred to as the limbus. This transitional zone is only 1mm wide and marks the point of insertion of the conjunctiva. It also contains tiny capillaries that nourish the cornea.