In hypoxic injury, cornea becomes edematous because of accumulation of:
Correct Answer: Lactate
Description: Ans. b. Lactate (Ref: Yanoff and Duker 4/e p280)In hypoxic injury, cornea becomes edematous because of accumulation of lactate.'Contact lenses are generally very well tolerated, but they induce numerous changes in corneal physiology and the tear film. Decreased oxygen tension occurs with contact lens wear, especially when conventional lenses are worn overnight. Hypoxic stromal edema results from the osmotic changes produced by lactate accumulation. - Yanoff and Duker 4/e p280CorneaCornea (the anterior surface) is the most important refractive surface of the eye, and have power of 45 diopter (3/4th of total power of eye). The refractive index is 1.376Q The critical angle is 46" at cornea tear interfaceThe healthy cornea is avascular and devoid of lymphatic channelsQ.Corneal cell derives nourishment by diffusion from the aqueous, the capillaries at the limbus and oxygen dissolved in the tear himQ.The metabolism of cornea is preferentially aerobicQ and it can function only up to 6-7 hours anaerobically under normal conditions.Hypoxic corneal stromal edema results from the osmotic changes produced by lactate accumulationQ.The metabolic active cells are endothelium, epithelium and stromal keratocytesQOxygen is mostly derived from tear filmQ with a small contribution from timbal capillaries.Glucose supply from cornea metabolism is mainly (90%) derived from aqueousQ and supplemented (10%) by limbal capillaries.Cornea is richly supplied by nervesQ (without myelin sheaths and Schwann cell sheath) which originate from small ophthalmic division of trigeminal nerve, mainly by long ciliary nerveQ Due to its dense nerve supply, the cornea is extremely sensitive structure.
Category:
Ophthalmology
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