A corneal abrasion is a cut or scratch on your cornea. The cornea is a clear layer of protective tissue at the front of your eye that lies over the iris (which is the colored part of your eye). The cornea helps focus light.
Corneal abrasions can occur when something gets into your eye, such as sand, dust, dirt, or other foreign objects. The cornea can also be scratched by a fingernail, a dirty contact lens, or by accidentally poking your eye. Another way an abrasion can occur is by rubbing your eyes too hard. In some people, the outer layers of the cornea are weak and they may suffer a corneal abrasion for no apparent reason.