Where Does Corneal Tissue Come From?
Eye tissue is acquired from an eye bank, which is a medical facility that obtains human eye tissue from donors for the purpose of corneal transplants, ophthalmic research, or educational training. Eye banks employ highly trained technicians to remove eye tissue from an individual who has designated their decision to donate at the time of death. The removal of the eye tissue from a donor is performed as soon as possible following death. Donor eye tissue is then procured and stored in a laboratory in the eye bank in a preservation medium under refrigeration. The technician carefully examines the cornea for defects and numerous tests are performed to ensure that there is no harm of transmitting diseases such as AIDS, or Hepatitis B and C viruses. All donors are carefully screened before the tissue is transplanted.
When is Surgery Needed?
Corneal transplants are necessary to restore vision if the following occurs:
- The surface of the cornea changes shape
- The cornea is scarred from a previous injury to the eye
- The layers become too thin
- Infections or inflammations of the cornea occur that lead to scarring
- Complications due to a previous eye surgery
- Certain inherited corneal dystrophies or degenerative processes
Some causes of these defects in the cornea may be attributed to various eye diseases known to affect and even destroy a healthy cornea. Keratoconus is a thinning disorder of the cornea where a cone-shaped protrusion forms. This abnormality prevents entering light rays from passing through the cornea properly.
About Corneal Transplant Surgery
Once a decision is made to proceed with corneal transplantation, the average waiting period for available cornea tissue may be several weeks. In addition to a physical exam, the ophthalmologist may request a few lab tests prior to surgery to be certain the patient is in good health. The physician may also administer antibiotic drops in the eye immediately before the patient’s surgery. A corneal transplant takes approximately one to two hours and can be done as an in-patient or out-patient service. Most ophthalmologists use a local anesthetic to numb the eye and prevent it from moving during surgery. The patient may be awake during the procedure, but will feel no discomfort. General anesthesia may also be used; the patient and the doctor can decide what is best for each situation. A trained ophthalmologist works through a microscope and uses a trephine (a circular surgical blade) to cut the donor tissue to the appropriate size for the transplant. The diseased tissue is removed and the donor tissue replaces it. A nylon stitch that is one-third the size of a human hair is used to suture the new tissue in its place. These stitches will remain in place until proper healing has occurred.