A scratch or defect in the epithelium (outer layer) of the cornea caused by a small, sharp particle in the eye (see eye, foreign body in) or by an injury. Corneal abrasions usually heal quickly but may cause severe pain and photophobia. Treatment includes covering the eye with a patch, analgesic drugs to relieve pain, and, if the eye muscles go into spasm, eyedrops containing cycloplegic drugs (which paralyse the ciliary muscle, preventing accommodation). Antibiotic eyedrops are usually
given to prevent bacterial infection, which can lead to a corneal ulcer.
The wearing away of tooth enamel, often accompanied by the erosion of dentine (the layer beneath the enamel) and cementum (the bonelike tissue that covers the tooth root), usually through too-vigorous brushing. Abraded areas are often sensitive to cold or hot food or drink, and a desensitizing toothpaste and/or protection with a bonding (see bonding, dental) agent or filling may be needed.... abrasion, dental
a white or greyish line in the periphery of the cornea, concentric with but separated from the edge by a clear zone. It begins above and below but may become a continuous ring. It consists of an infiltration of fatty material and is common in the elderly (arcus senilis). When it occurs in younger people (arcus juvenilis) it may indicate *hyperlipidaemia. It does not affect vision.... corneal arcus
reflex blinking of both eyes normally elicited by lightly touching the cornea of one eye. This reflex is lost in deep coma, during general anaesthesia, and in death; it is therefore one of the tests used to confirm brainstem death.... corneal reflex
a ring designed to be inserted into the peripheral tissue of the cornea in order to alter the curvature of the corneal surface. It is undergoing trials to assess its ability to correct errors of refraction. In myopia (short-sightedness), for example, the ring would be required to stretch the corneal tissue peripherally and thus flatten the central corneal curvature in order to correct the myopia.... corneal ring