Natural Involution of Acute Retinopathy of Prematurity Not Requiring Treatment: Factors Associated With the Time Course of Involution

Abstract

PURPOSE: We identified the timing of natural involution of acute retinopathy of prematurity (ROP) not requiring treatment and determined the risk factors associated with delayed involution. METHODS: In this retrospective case series, 82 eyes (the more severe eye) of 82 infants who developed at least one clock hour of acute ROP, stages 1 through 3, but who didn't progress to type 1 ROP, were selected for analysis. The location, extent, and severity of ROP were documented by investigators during serial retinal examinations. The onset and completion of the ROP's involution were determined from a review of these data. Two groups were classified by the involution pattern: Group 1 included infants whose ROP disease involuted before 50 weeks of postmenstrual age, and Group 2 included infants whose ROP disease involuted over 50 weeks (delayed involution). A total of 14 possible risk factors was included in the logistic regression analysis to assess the relationship between each factor and the involution pattern. RESULTS: Acute ROP not requiring treatment began to involute at a mean of 40.4 weeks of postmenstrual age and finished at a mean of 50.6 weeks. Involution began at the same mean postmenstrual age for each zone of disease (P = 0.48) and finished earlier in zone III than in zone II (P < 0.01). An analysis by severity of ROP found that involution began the earliest with the mildest disease (stage 1; mean, 38.1 weeks) and latest with the most serious disease (stage 3; mean, 42.3 weeks; P < 0.01). Zone II disease took longer to finish involution (16.04 ± 12.35 weeks) than zone III (8.30 ± 7.3 weeks), and stage 3 (23.88 ± 10.58 weeks) took longer to finish involution than stage 1 (2.03 ± 0.96 weeks) and stage 2 disease (7.69 ± 4.75 weeks, P < 0.01, respectively). No unfavorable outcome was found in our series. Multivariable logistic regression analysis showed that continuous positive airway pressure (CPAP, P < 0.0001), active stage 3 disease (P = 0.006), and anemia (P = 0.03) were significant risk factors associated with delayed involution. CONCLUSIONS: The natural involution of acute ROP not requiring treatment correlated better with severity than with ROP location. Active stage 3 disease, CPAP, and anemia were predictive risk factors for delayed involution of ROP.