Corneal epithelial ulceration and erosion can result from many causes, including physical trauma, contact with irritating chemicals via direct topical administration, contact with systemic toxicants secreted by the lacrimal glands into the precorneal tear film, exposure to ionizing radiation or excess ambient light, and reduced blinking reflex or eyelid closure due to prolonged anesthesia or deficits of eyelid innervation. Corneal epithelial ulcers and erosions can also be sequelae of corneal inflammation or alterations in the precorneal tear film composition due to lacrimal gland disease.
Although less common than epithelial changes, ulceration of the single-layered corneal endothelium (lining the posterior surface of the cornea) can also occur. Corneal epithelial erosions, in which there is partial epithelial denudation with retention of an intact basal lamina, are similar lesions, though typically less extensive.
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