How are donated corneas screened for herpes zoster virus before they can be used for transplants?

Leigh

A corneal transplant involves surgically replacing a damaged cornea with a healthy cornea donated by someone who has died. Common causes of corneal damage that can require a corneal transplant include infections such as herpes, eye trauma, inherited eye diseases and corneal shape disorders such as keratoconus.

During the one- to two-hour transplant operation, surgeons remove the diseased cornea and suture in a donated cornea. While the surgical procedure itself is relatively simple, the recovery period can be lengthy. It can take a patient four to eight months (or even longer) to experience significant vision improvement. The main reason for this delay is that the new cornea initially has an irregular shape and it takes time for the cornea to smooth out, allowing for better vision.

Obviously, it is vital that a donated cornea be healthy and disease-free. The Eye Bank Association of America has developed medical standards to limit the risk of accidental transmission of infectious diseases from the donor to the recipient. These criteria include eliminating potential donors if they have died from infectious diseases such as AIDS, viral hepatitis, rabies, viral encephalitis, syphilis or Creutzfeldt-Jakob disease.

Herpes zoster (also called shingles) is caused by the same virus that causes chickenpox, and it occurs only in people who have had chickenpox in the past. Herpes zoster erupts when the virus remaining in the body becomes active again, which may be years to decades after the original chickenpox infection. It is most commonly characterized by a localized outbreak of a skin rash with severe pain. If herpes zoster affects the eye, it can cause corneal scarring and eye inflammation.

A person who has an eye infected with herpes zoster will generally have scarring of the cornea -- and lab technicians who "grade" donated corneas are trained to reject those that are scarred. If a cornea scarred by herpes zoster were to slip past the official corneal graders, the corneal surgeon would most likely notice the corneal scarring before the surgery and not transplant that cornea. As far as I am aware, there have been no documented cases of herpes transmission from a cornea donor to a cornea recipient.