Anatomy & Physiology
Major Ocular Structures

The cornea consists of five distinct layers. These include the Epithelium, Bowman�s Membrane, Stroma, Desemet�s Membrane, Endothelium. The corneal epithelium is highly regenerative. The cells reproduce so rapidly that a mild scratch or abrasion of the cornea can heal itself within 24 hours. This is not true of the other corneal layers. Overall, the cornea is about 0.5mm thick at its center with the stroma comprising 90% of the total thickness. Knowledge of corneal physiology becomes especially important when dealing with contact lenses.

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Cones	Rods
Day Vision	Night Vision
Detail	Peripheral Vision
Color	Black and White

Each retina contains about 120 million rods and 6 million cones. The greatest density of cones are found in the fovea. Radiating outwardly from the fovea, the population of cones gradually decreases while the population of rods increases. The chart above summarizes the function of each of these types of receptors.