Cold probe reduces preemie blindness.

Cold probe reduces preemie blindness

A procedure that freezes the surface of the eye can cut by half the risk of "severe vision loss" among premature infants with the vision-threatening disease called retinopathy of prematurity, scientists said this week in announcing a recently completed study at 23 U.S. medical centers.

A disease that causes vision loss in 2,600 U.S. infants annually, the retinopathy is caused by abnormal branching of blood vessels in the underdeveloped eye that intertwine and prevent normal vessel growth throughout the retina, which lines the eye's interior. Eventually, if the condition does not spontaneously reverse itself (which occurs in about 50 percent of cases), the retina becomes detached, causing either total or partial blindness. But, say the scientists, if the area is frozen, the progression to blindness often can be halted by removing barriers to normal growth.

Sponsored by the National Eye Institute in Bethesda, Md., the study of 172 very low birthweight infants (below 2.76 pounds at birth) with early stages of the disease found that a probe cooled to 80 degrees C -- when touched to the outside of the eyeball -- apparently removes the twisted abnormal vessels. "Each ~frozen| spot is two to three millimeters in diameter, and approximately 50 of them are distributed like polka dots in a belt around the front part of the retina," says Earl A. Palmer of Oregon Health Sciences University in Portland, chairman of the study. He and other researchers presented the results this week at a news briefing.

In the study, one eye was treated, the other left untreated. In the treated eyes, only 21.8 percent progressed to an "unfavorable outcome," compared to 43 percent of untreated eyes. An unfavorable outcome was defined as retinal detachment of folding. A favorable outcome, says Palmer, means the infant will likely have better vision than that considered legally blind. He says that no significant side effects were noted during the study, but that the technique will likely cause some loss of peripheral vision due to scarring. Not all infants are candidates for cryotherapy -- but when it is used, timing is critical, says Palmer, because it is too late once the retina detaches.

Because of the dramatic results, which will appear in the April ARCHIVES OF OPHTHALMOLOGY and the May PEDIATRICS, a monitoring committee halted the study before its original completion date. On Feb. 12, study coordinators mailed a "clinical alert" to 2,300 specialists in the United States, recommending referral of patients to one of the 23 participating centers until publication of the final results. Although the therapy has been used for years in other countries -- in Japan since 1972 -- with apparent success, Palmer says U.S. clinicians did not adopt the procedure pending more definitive results of a large, controlled clinical trial like the one just completed.