Natural involution of acute retinopathy of prematurity not requiring treatment: factors associated with the time course of involution.

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.