Objective: To evaluate monocular contrast sensitivity (CS) at age 10 years in eyes that underwent cryotherapy and in control eyes of participants in the randomized trial of cryotherapy for retinopathy of prematurity (CRYO-ROP), and in a comparison group of 10-year-old low-birth-weight children who did not develop ROP in the neonatal period.
Methods: Eligible participants were the 255 survivors of the group of 291 infants with severe (threshold) ROP in 1 or both eyes who were enrolled in the randomized CRYO-ROP trial as neonates, as well as 104 children in the CRYO-ROP study who did not develop ROP. All had birth weights less than 1251 g. Contrast sensitivity was measured using Pelli-Robson charts at a test distance of 1 m with luminance at or higher than 64 candelas (cd)/m(2). Contrast sensitivity was estimated using the total number of letters identified.
Results: Unfavorable CS outcomes (<27 letters identified) were found in a greater proportion of control eyes (59.3%) than of treated eyes (39.7%) (P<.001). In patients with bilateral threshold ROP who had quantifiable CS in both eyes, CS results were similar in treated and control eyes, suggesting no detrimental effect of cryotherapy. In the "no ROP" group, 96.9% of eyes showed CS in the normal range, compared with 48.1% of treated eyes and 34.6% of control eyes.
Conclusions: The results further confirm the beneficial effect of cryotherapy on visual function, and show no evidence of adverse effects of cryotherapy on CS. With or without cryotherapy, eyes with severe ROP showed substantially poorer CS than did eyes of preterm children who did not develop ROP.