title: Multicenter trial of cryotherapy for retinopathy of prematurity. Snellen visual acuity and structural outcome at 5 1/2 years after randomization.
abstract: OBJECTIVE
  To evaluate outcome at 5 1/2 years after randomization in eyes that underwent cryotherapy and in control eyes of patients in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity.
  
  
  METHODS
  During infancy, patients with bilateral threshold retinopathy of prematurity (ROP) were assigned to receive cryotherapy for one eye and no cryotherapy for the other eye. Those with threshold ROP in only one eye (asymmetric) were randomly assigned to cryotherapy or no cryotherapy for that eye. Then, 5 1/2 years later, testers who were masked to the treatment status of each eye measured the patients' monocular visual acuity by using the log of the minimum angle of resolution visual acuity chart that was used in the Early Treatment of Diabetic Retinopathy Study. This was the most refined visual acuity testing yet performed on this cohort. Structural outcome was evaluated by participating ophthalmologists' assessment of ROP residua in the posterior pole of the fundus.
  
  
  METHODS
  Patients were 291 children who had been preterm infants with birth weights of less than 1251 g in whom threshold ROP had developed. Two hundred forty patients had bilateral threshold ROP, and 51 had threshold ROP in only one eye.
  
  
  RESULTS
  For the 234 children examined, both visual acuity and fundus structure showed a reduction in unfavorable outcomes in treated vs control eyes: 47.1% vs 61.7%, respectively (P<.005), for visual acuity and 26.9% vs 45.4%, respectively (P<.001), for fundus status. Detailed analysis of visual acuity outcomes for all eyes revealed that while fewer treated eyes (31.5%) than control eyes (48%) were blind (P<.001), there was a slight trend toward fewer eyes with a visual acuity of 20/40 or better in the treated (13%) vs control (17%) groups (P=.19).
  
  
  CONCLUSIONS
  The results support the long-term efficacy and safety of cryotherapy in the treatment of severe ROP. However, the data show preliminary evidence of a possible adverse effect of this treatment on visual acuity.
authors.affiliation: Casey Eye Institute, Oregon Health Sciences University, Portland, OR, USA.
mesh_terms: D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003452:Cryosurgery; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D012163:Retinal Detachment / Q000503:physiopathology / Q000601:surgery; D012178:Retinopathy of Prematurity / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome; D014792:Visual Acuity