Corneal abrasions are scratches on the surface of the cornea resulting in loss of corneal epithelium, the modified skin layer lining the front of the eye. Underlying corneal nerves are exposed to the elements and the condition can be extremely painful. Corneal abrasions usually occur as a result of trauma to the eye. Common examples including a baby’s finger, paper, gardening or from a piece of grit getting in the eye. Occasionally, the patient cannot recollect any such incident. The condition can take 24 to 48 hours to improve as new corneal epithelium slides across to cover the defect. Until this time, the best treatment is simply to keep the eye closed as the action of blinking slows the rate of epithelial repair slightly. Usually we use an antibiotic containing ointment as this may speed recovery, reduce pain slightly and prevent infection, although infection is exceedingly rare after a corneal abrasion.
Like abrasions, these result in defects of the corneal epithelium, but can occur without a history of trauma. They tend to be localised on the inferior cornea just below the pupil, be larger, more painful and take longer to heal than corneal abrasions. Particularly in the absence of trauma, there may be underlying disorder of the corneal epithelium and this can predispose the patient to recurrent attacks. These typically occur first in the morning when the patient opens his or her eye for the first time. Occasionally, a patient is woken in the middle of the night in great pain. This might be related to the onset of rapid eye movement sleep. It is likely that these erosions are caused by the eyelid sticking to the corneal epithelium, which shears off on eye or lid movement. Symptoms can often be improved by the application of ointment to the eye last thing at night as the greasy barrier provided by the ointment reduces direct lid/corneal epithelium contact.