Corneal Abrasion Health Article

Definition

A corneal abrasion occurs when there is a loss of cells from the epithelium or surface of the cornea. It is usually due to trauma but may occur without trauma such as with the overuse of contact lenses.

Description

The cornea is the clear curved structure found at the front of the eye. It is comprised of three layers and the membranes that separate these layers. It is very difficult to penetrate past the epithelium or top layer of the cornea. The cornea is normally devoid of blood vessels yet has many sensory nerves. When any trauma to the corneal epithelium occurs, cells are lost or destroyed and pain is immediately sensed. When a corneal abrasion occurs, the conjunctiva, or the white of the eye, turns red, as new blood vessels form and those present enlarge, in an attempt to increase blood flow to the eye as it attempts to bring to the eye those cells needed for the healing of the cornea.

A corneal abrasion heals by the movement of neighboring epithelial cells, which slide over the wounded area, and through a cell division process called mitosis, which fill in the abraded area with new epithelial cells. Within two to three days of trauma to the cornea, these new cells start to adhere to the underlying membrane of the epithelium, called the basement membrane and within seven to eight days the abraded area usually heals completely without scarring. But if a corneal abrasion is deep and penetrates the next layer of the cornea, then scarring is possible and complete healing of the abrasion may be delayed as long as three months.

Demographics

Corneal abrasions account for 10 percent of ocular emergency care. The incidence of non-penetrating injuries to the eye, which includes corneal abrasions, is 1.57 percent per year. More males are treated for corneal abrasions than are females.

Causes and symptoms

Common causes of corneal abrasions include fingernails, make-up implements, paper cuts, plant material, including tree branches, animal scratches, cigarettes, inverted eyelashes, and blunt trauma, such as that with a knife or with scissors. Children are most likely to get a corneal abrasion while playing, while adults are more likely to sustain an abrasion in the workplace. Ultraviolet radiation such as that which occurs with a welder's flash or use of a sunlamp, can also cause an abrasion, as well as misuse and mishandling of contact lenses. When a missile type object causes an abrasion, the object can become embedded in the cornea or penetrate the eye.

Pain, irritation, tearing, red eye, twitching of the eye, decreased vision, and sensitivity to bright lights are common complaints that accompany a corneal abrasion. If there is significant swelling of the cornea, then vision may be decreased. If there is inflammation inside the eye, a dull ache may be felt inside the eye. Very rarely, nausea is experienced due to the pain associated with a corneal abrasion. The only symptom in a nonverbal patient, such as an infant, may be that the child is fussier than usual.

When to call the doctor

Any redness or foreign body sensation, especially if only one eye is affected, should be evaluated promptly for a corneal abrasion. If a corneal abrasion is not treated appropriately, scarring and ulceration of the corneal are possible. A corneal abrasion should be treated by a healthcare practitioner capable of evaluating eye conditions. Herpes simplex, recurrent corneal erosion (RCE), and acanthamoeba infections are other conditions that can mimic a corneal abrasion but which require very different treatments.

Diagnosis

The individual with a corneal abrasion will usually report a known trauma to the eye area.

To diagnose a corneal abrasion, a topical anesthetic with a yellow dye called flourescein is placed into the eye. Under blue cobalt light, the part of the cornea abraded will be stained by the dye and is easily seen by the examiner. The area and depth of the abrasion can be easily seen under a special microscope called a slit lamp biomicroscope. If a microscope is not available, then a blue light called a Burton lamp may be used.

Usually the anesthetic drop will relieve the ocular pain immediately. If a dull aching sensation persists after this instillation then a co-existing iritis, or inflammation of the iris, also called a uveitis, may also be present. When a biomicroscope is available, the eye is checked for infection or inflammation. The eyelids are everted (turned out) to check for any foreign bodies. These areas may also be rinsed with saline to remove any small foreign body that may be a source of the abrasion.

If any of the instilled dye leaks into the eye, then the cornea has been perforated and a small projectile may be inside the eye. Other testing, such as x rays, must be done to rule out foreign bodies inside the eye. Since metal is the most common material seen in penetrating injuries, an MRI is not usually done. If the cornea has been perforated, then the patient is referred to a corneal specialist for surgery.

If an infection is suspected or if an abrasion does not heal, then swabbing of the eye for microscopic culture may be done to definitively establish the organism involved.