The purpose of the proposed study is to examine the long-term structural and functional effects of cryotherapy as a treatment for severe retinopathy of prematurity (ROP). In the initial phase of the study, eyes with 5 contiguous or 8 total clock hours of stage 3 ROP with plus disease, from 291 infants with birth weights less than 1251 g., were randomized to receive cryotherapy or no cryotherapy. Follow-up to age 12 months during Phase II of the study indicated that cryotherapy reduced the incidence of unfavorable structural outcome by 45.8 percent and the incidence of unfavorable visual acuity outcome by 37.8 percent. Based on the preliminary data, follow-up to age 12 months during Phase II of the study indicated that cryotherapy reduced the incidence of unfavorable structural outcome by 39.1 percent. Cryotherapy reduced the incidence of unfavorable functional outcome by 21.4 percent, based on measurement of resolution acuity, and by 19/7 percent, based on measurement of recognition acuity. The present study proposes to follow patients in the randomized group and a small subgroup (67 infants) of potentially high risk infants from the Natural History Study through age 10 years, to determine whether the reduction in the benefit of cryotherapy seen between ages 12 and 42 months continue into mid- childhood. Evaluation of the benefit of cryotherapy will be based on examination of the posterior pole and on assessment of visual acuity, as in Phase II. In addition, a more complete evaluation of visual function will be conducted, through assessment of monocular contrast sensitivity, monocular color vision, and stereopsis at age 9 years, and through measurement of visual field extent with the Goldmann perimeter at age 10 years.
