Blind World

Laser therapy outpaces cryotherapy for treating ocular disease in 10-year study.

June 14, 2002.

BY Sonia Nichols,
Angiogenesis Weekly.

Follow-up evaluations of patients treated for retinopathy of prematurity show that overall, laser therapy yields better outcomes than cryotherapy does.

Retinopathy of prematurity is a disease causing misplacement or malformation of the retina by overgrown blood vessels that develop as a result of excess oxygen. Premature infants weighing fewer than 3 pounds who are placed in high-oxygen environments after being born are typically candidates for this disorder. Like other ocular diseases, it can be treated, to some degree, with laser photocoagulation or cryotherapy. Doctors at Wills Eye Hospital in Philadelphia, Pennsylvania, recently reported their findings after completing a 10-year study of 25 patients with 44 eyes that were randomly assigned to receive one of the treatment methods after being diagnosed with retinopathy of prematurity. Sixty-six patients were originally enrolled in the clinical trial.

Using standard tools for assessing vision and ocular pathology, the group, headed by William Tasman, reported follow-up data and noted treatment that had been rendered for strabismus or amblyopia during the intervening years.

Usually, having a value of 20/20 on the Snellen test without the use of corrective appliances is considered perfect vision. "Eyes treated with laser had a mean best-corrected ETDRS visual acuity (BCVA) of 20/66 (Snellen equivalent), whereas cryotherapy-treated eyes had a mean BCVA of 20/182 (Snellen equivalent) (p=0.015, n=42)," said Eugene Y.J. Ng, a project collaborator from the National University of Ireland in Dublin, Ireland.

Moreover, having 20/50 or better BCVA was over than five times more likely in those who had been treated with laser photocoagulation than in those treated with cryotherapy, the researchers said (A comparison of laser photocoagulation with cryotherapy for threshold retinopathy of prematurity at 10 years, Ophthalmology, 2002;109(5):928-934).

In contrast, eyes treated with cryotherapy were significantly more likely to develop retinal dragging, and statistical analysis showed there was a proportional and inverse relationship between degree of retinal dragging and extent of visual acuity.

During the intervening years between treatment and follow-up, several of the patients had been diagnosed with and/or treated for strabismus and amblyopia.

"Overall, laser-treated eyes had better structural and functional outcome compared with eyes treated with cryotherapy," Tasman's team proposed.

The corresponding author for this study is William S. Tasman, MD, Ophthalmologist-in-Chief, Wills Eye Hospital, 900 Walnut Street, Philadelphia, PA 19107, USA.

Key points reported in this study include:

*Visual acuity was significantly better in retinopathy of prematurity patients treated with laser photocoagulation at 10-year follow-up

*Retinal dragging was more pervasive in these patients when treated with cryotherapy, at 10-year follow-up

*Overall outcomes were better in retinopathy of prematurity patients treated with laser therapy than cryotherapy at 10-year follow-up

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