Icy Cure

Cryotherapy -- literally, treatment by extreme cold -- is particularly valuable in ophthalmology. It has already destroyed eye tumors, removed cataracts and sealed lesions in the retina. Now Dr. John Bellows of Northwestern University reports that it is highly effective in the treatment of a viral infection of the eye called herpetic keratitis.

The same virus that causes simple cold sores on the lip--herpesvirus--can also attack the surface of the eye; if unchecked, it can do damage that will scar the cornea, resulting in partial or complete blindness. The best treatment has hitherto proved successful in only 60% of cases, and the disease ranks as the commonest infection causing corneal scarring. Faced with cases that seemed beyond help, Dr. Bellows decided to try a cryoprobe chilled to a temperature of -- 65DEGC.

His method is so simple that, in most cases, it can be carried out under a local anesthetic in the doctor's office. The patient is told to fix his gaze on a distant object. Then, while his eyelid is held open, the icy tip of the pencil-size probe is applied to every part of the diseased section for seven seconds at a time. The area is thawed each time with a salt solution to unstick the probe and eye, which freeze together after the fashion of a finger on an ice tray. After the thaw, the entire procedure is repeated twice more. In early cases, the eye should regain its normal luster in four days, with little pain either during or after the treatment.

The severe freezing, hypothesizes Dr. Bellows, "causes disruption of the infected cells. These disrupted cells release a high concentration of interferon," a natural virus fighter. Most of the herpesvirus is killed outright by the cold, and the interferon is able to stop the spread of whatever remains, eventually allowing it all to be killed. "The response to cryotherapy is so uniformly satisfactory," says Dr. Bellows, "that in unresponsive cases the physician should question the diagnosis and re-examine the patient."

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