Does cryotherapy affect refractive error? Results from treated versus control eyes in the cryotherapy for retinopathy of prematurity trial

Purpose: To evaluate the effect of cryotherapy on refractive error status b etween ages 3 months and 10 years in children with birth weights of less th an 1251 g in whom severe retinopathy of prematurity (ROP) developed in one or both eyes during the neonatal period. Design: Randomized clinical trial. Participants: Two hundred ninety-one children in whom severe ROP developed during the neonatal period. Intervention: Cryotherapy for ROP. Main Outcome Measures: Cycloplegic Refraction Methods: The children underwent repeated follow-up eye examinations, includ ing cycloplegic retinoscopy, between 3 months and 10 years after term due d ate. Refractive error data from all eyes that were randomized to cryotherap y were compared with data from ail eyes that were randomized to serve as co ntrols. Refractive error data were also compared for a subset of children w ho had both a treated and a control eye that could be refracted. Results: At all ages, the proportion of treated eyes that were unable to be refracted because of retinal detachment, media opacity, or pupillary miosi s was approximately half the proportion of the control eyes that were unabl e to be refracted. When data from all eyes that could be refracted were con sidered, the distribution of refractive errors between fewer than 8 diopter s (D) of myopia and more than 8 D of hyperopia was similar for treated and control eyes at all ages. The proportion of eyes with 8 D or more of myopia was much higher in treated than in control eyes at all ages after 3 months . In the subset of children who had a treated eye and a control eye that co uld be refracted, distributions of refractive errors in treated versus cont rol eyes were similar at most ages. Conclusions: In both treated and control eyes, there was an increase in the prevalence of high myopia between 3 and 12 months of age. Between 12 month s and 10 years of age, there was little change in distribution of refractiv e error in treated or control eyes. The higher prevalence of myopia of 8 D or more in treated eyes, as compared with control eyes, may be the result o f cryotherapy's preservation of retinal structure in eyes that, in the abse nce of cryotherapy, would have progressed to retinal detachment. Ophthalmol ogy 2001;108:343-347 (C) 2001 by the American Academy of Ophthalmology.