title: Involution of retinopathy of prematurity. Cryotherapy for Retinopathy of Prematurity Cooperative Group.
abstract: OBJECTIVE
  To report the timing of involution of acute retinopathy of prematurity (ROP).
  
  
  METHODS
  An analysis of prospective retinal observational data recorded at infants' eye examinations.
  
  
  METHODS
  Infants from the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) had birth weights less than 1251 g and served as subjects. The study population included 766 children who were examined in 5 of the 23 study centers and who developed at least 1 clock hour of acute ROP, stages 1 through 3. One eye from each patient was randomly chosen for analysis.
  
  
  METHODS
  Investigators documented the location, extent, and severity of ROP during serial retinal examinations. The onset of the ROP's involution was determined from a review of these data, applying a set of predetermined criteria.
  
  
  RESULTS
  Acute-phase ROP began to involute at a mean of 38.6 weeks postmenstrual age. In 90% of patients, the ROP began to involute before 44 weeks of postmenstrual age. Acute ROP that demonstrated involution by moving from zone II to zone III was associated with an unfavorable outcome in 2 (1%) of 200 cases. Retinopathy of prematurity that was present only in zone III during a child's serial retinal examinations was never associated with the development of a partial or total retinal detachment.
  
  
  CONCLUSIONS
  The onset of involution of acute retinopathy of prematurity correlates better with postmenstrual rather than with chronological age. This is reminiscent of the reported similar correlation of postmenstrual age to the time of onset of prethreshold and threshold ROP. Zone III ROP was nearly always associated with a favorable outcome.
authors.affiliation: Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287-9028, USA. mrepka@jhmi.edu
authors.forename: M X
authors.initials: MX
authors.lastname: Repka
authors.forename: E A
authors.initials: EA
authors.lastname: Palmer
authors.forename: B
authors.initials: B
authors.lastname: Tung
mesh_terms: D000208:Acute Disease; D001724:Birth Weight; D003452:Cryosurgery; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D011446:Prospective Studies; D012178:Retinopathy of Prematurity / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery; D012720:Severity of Illness Index; D013997:Time Factors