Eye Q: Cornea
What is a corneal abrasion and how is it treated?
The cornea is the outer clear window on the surface of the eye. Like any body surface that’s exposed to the environment, it has a layer of skin cells overlying it. Any time the skin cells are disrupted or removed by injury, the result is a corneal abrasion. The symptoms of this condition are extreme pain, light sensitivity and tearing. These symptoms drive the majority of patients to visit an eye care practitioner. The typical findings are that of an area in which the skins cells have been disrupted with an underlying clear cornea. Treatment is to reduce symptoms, as the skin usually will heal from the sides of the disrupted area in toward its center in one to two days. Because the symptoms are severe, several treatments are used to reduce these symptoms and to assist in healing. The abrasion could become infected, so the majority of treatments include antibiotic drops or ointment. It is quite rare that an abrasion would result in scarring of the cornea.
Who needs a corneal transplant?
The majority of the thickness of the cornea is composed of a perfectly aligned array of collagen fibers, a few cells, some space-filling molecules elaborated by the cells, and water. The cornea needs to maintain just the right balance of water within its substance. The two main reasons people need corneal transplantation are irregular shape of the cornea or opacification or haziness of the cornea. Irregular shape of the cornea means that the normal, round, smooth shape of the cornea is distorted and has become more like that of the end of an egg. This reduces the ability of light rays to pass through the cornea and be adequately brought to a single focal point in the eye. When this can no longer be corrected with contact lens alone, patients would then need to consider corneal transplantation. Scar formation from injury and increased water retained within the cornea are two reasons haziness or opacification can occur. Either of these could be considerable enough so that vision is compromised and would also result in a corneal transplant.
Transplantation of the cornea is performed by using tissue donated and recovered from people who die throughout the state of Wisconsin. Families consent to donation. Tissues are recovered and processed through the Lions Eye Bank of Wisconsin and made available to surgeons across the state. Once a decision is made for replacement of the cornea, the traditional transplant is performed by removing the central full thickness of the patient’s cornea, replacing it with a similar size piece of cornea from the donor and placing stitches to hold this securely. The healing process takes many months and over that time, stitches gradually need to be removed. While the transplanted cornea often remains clear for a number of years, it is very common for its healing to be associated with high amounts of irregularity on its surface so that strong glasses or contact lens are often needed for best vision. For corneal opacity secondary to the swelling of the cornea a newer type of transplantation is available. No stitches are required and only the inner back portion of the cornea is replaced. This area is most responsible for keeping the cornea with just the right balance of water. Many times, for either type of corneal transplant, cataract surgery or removal of the cloudy lens of the eye is performed at the same time.