Transparent Structures of the Eyeball Cornea, Lens, and Vitreous
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The eyeball resembles a ping-pong ball with a transparent dome in the front called the cornea. The cornea constitutes one-sixth of the eyeball; the posterior five-sixths are formed by the scleral shell. The cornea is thin in the center and thick at the periphery. Superiorly and inferiorly it is encroached upon by the sclera in a crescentic way, thus reducing the frontal vertical diameter. It is circular in outline; the periphery merges with the sclera, and the junction is called the limbus. Its front surface is covered by a three-layered tear film that keeps it moist and smooths the microscopic irregularity of its outermost layer: the corneal epithelium. That smooth surface is necessary for proper refraction at the cornea.
KeywordsTransparent dome Cornea Bowman’s membrane Tear film Descemet’s membrane Dehydrating pump Endothelium Superficial keratitis Deep keratitis Capsule of lens Differential thickness Zonule Accommodation Smoothing action of tear film for microscopic irregularities of corneal epithelium Optimum width of angle of anterior chamber Senile cataract Nutrition of cornea and lens by normal aqueous
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