title: Does cryotherapy affect refractive error? Results from treated versus control eyes in the cryotherapy for retinopathy of prematurity trial.
abstract: OBJECTIVE
  To evaluate the effect of cryotherapy on refractive error status between ages 3 months and 10 years in children with birth weights of less than 1251 g in whom severe retinopathy of prematurity (ROP) developed in one or both eyes during the neonatal period.
  
  
  METHODS
  Randomized clinical trial.
  
  
  METHODS
  Two hundred ninety-one children in whom severe ROP developed during the neonatal period.
  
  
  METHODS
  Cryotherapy for ROP.
  
  
  METHODS
  Cycloplegic Refraction
  
  
  METHODS
  The children underwent repeated follow-up eye examinations, including cycloplegic retinoscopy, between 3 months and 10 years after term due date. Refractive error data from all eyes that were randomized to cryotherapy were compared with data from all eyes that were randomized to serve as controls. Refractive error data were also compared for a subset of children who 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 miosis was approximately half the proportion of the control eyes that were unable to be refracted. When data from all eyes that could be refracted were considered, the distribution of refractive errors between fewer than 8 diopters (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 could be refracted, distributions of refractive errors in treated versus control 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 months and 10 years of age, there was little change in distribution of refractive 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 of cryotherapy's preservation of retinal structure in eyes that, in the absence of cryotherapy, would have progressed to retinal detachment.
authors.affiliation: Division of Pediatric Ophthalmology, The Children's Hospital of Philadelphia, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA.
authors.forename: G E
authors.initials: GE
authors.lastname: Quinn
authors.forename: V
authors.initials: V
authors.lastname: Dobson
authors.forename: R
authors.initials: R
authors.lastname: Siatkowski
authors.forename: R J
authors.initials: RJ
authors.lastname: Hardy
authors.forename: J
authors.initials: J
authors.lastname: Kivlin
authors.forename: E A
authors.initials: EA
authors.lastname: Palmer
authors.forename: D L
authors.initials: DL
authors.lastname: Phelps
authors.forename: M X
authors.initials: MX
authors.lastname: Repka
authors.forename: C G
authors.initials: CG
authors.lastname: Summers
authors.forename: B
authors.initials: B
authors.lastname: Tung
authors.forename: W
authors.initials: W
authors.lastname: Chan
mesh_terms: D001251:Astigmatism / Q000175:diagnosis / Q000209:etiology*; D002648:Child; D002675:Child, Preschool; D017679:Cryotherapy / Q000009:adverse effects*; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009216:Myopia / Q000175:diagnosis / Q000209:etiology*; D015995:Prevalence; D012029:Refraction, Ocular; D012163:Retinal Detachment / Q000209:etiology; D012178:Retinopathy of Prematurity / Q000150:complications / Q000601:surgery*; D014792:Visual Acuity