What is the Cornea?
The cornea is the clear, front window of the eye, much like the crystal on your wristwatch. Light rays pass through the cornea, and are focused on the retina (in the back of the eye). Many eye conditions may affect the cornea and change its transparency. Corneal clouding is much like a frosted window pane, thus blocking the clear passage of light to the back of the eye. Reduced sight, sometimes even to the point of blindness, may result. Sometimes corneal injury and disease can be very painful as well.
What are the Causes?
There are many causes of corneal clouding. Injuries may cause scarring of the cornea from fireworks, exploding batteries, toxic chemicals (such as acids and alkalis), and sharp objects (such as knives and pencils).
Most of these types of corneal injuries are preventable with protective glasses and proper precautions when dealing with hazardous substances. Infections, whether bacterial, fungal, or viral (such as herpes simplex), are frequent causes of severe corneal damage and ulcerations, and may result in corneal scarring. Abnormal steepening of the cornea (keratoconus), degeneration following cataract surgery, (corneal edema or swelling), and some aging processes (such as Fuchs’ corneal dystrophy) can also affect the clarity and health of the cornea. Moreover, some disorders of the cornea are inherited and can lead to corneal clouding and loss of sight in children or young adults. What can be Done? Sometimes the vision may be improved with glasses, a contact lens, or medications.
However, in many cases, a corneal transplantation is necessary to restore sight. Corneal transplantation (keratoplasty) is the most successful of all tissue or organ transplants. Nearly 30,000 corneal transplants are done each year in the United States. The success rate of corneal transplantation depends on the cause of the corneal clouding. For example, corneal transplantation for degeneration or swelling and those for keratoconus, both have high success rates (approximately 90%), while corneal transplants for chemical burns have lower success rates (approximately 65%). Corneal tissue for transplantation comes from an Eye Bank.
The process begins with the recent death of someone who has been generous enough to be a corneal donor. Names of patients needing corneal transplants are placed on a waiting list until tissue is available. The health of the donor material is carefully inspected before it is used for corneal transplant. If the material is not suitable in any way, it is not used for the transplant. In addition, the donor is tested for hepatitis and AIDS to make sure that these infections will not be transmitted by the corneal transplant. To protect the privacy of the donor and his family, the details of the donation cannot be revealed. The donor corneal tissue is usually used within a few days following the death of the donor.