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FIGURE 8-1 Anatomy of the eye.

regularly oriented and contribute significantly to corneal clarity. The inner surface of the cornea is lined with a single layer of endothelium, a metabolically active cellular layer that pumps electrolytes, water, and metabolites out of the cornea. The corneal epithelium is derived from a specific group of stem cells, encircling the cornea, that multiply and ultimately form mature corneal cells. A different population of stem cells, in the conjunctival fornices, give rise to the conjunctival epithelium.

Corneal nutrition is supplied almost exclusively by the aqueous humor circulating behind the cornea in the front of the eye. This allows the cornea to obtain its nutrition in the absence of blood vessels, an obvious aid to clarity. When blood vessels do enter the cornea (in disease or injury), scarring occurs, with a loss of transparency and consequently loss of vision.

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