Predictive value of age, angle, and refraction on rate of reoperation and rate of spontaneous resolution in infantile esotropia.

UNLABELLED: In the Early vs. Late Infantile Strabismus Surgery Study (ELISSS), 13.5% of children operated at 20 months vs. 3.9% of those operated at age 4 had gross binocular vision (Titmus Housefly). Reoperation rates were 28.7% in the former vs. 24.6% in the latter group and, although all were eligible for surgery at baseline at 11 SD 3.7 months, 8% in the early group vs. 20% in the late group were never operated, mostly because their angle decreased spontaneously. We assessed the predictive value of age, angle, and refraction in these matters.

METHODS

The ELISSS reoperation rates were first compared with those found in nine series of consecutive cases in nine university clinics operated during one particular year, between 6 and 23 years previously. Logistic regression was used to estimate the effect of postoperative angle and clinic on the chance of reoperation. Secondly, a meta-regression analysis was done of these and other reported reoperation rates. The mean age at operation and the mean duration of follow-up were regressed on the logistically transformed reported reoperation rates. Finally, to estimate the chance of spontaneous decrease of the angle without surgery, a random-effects model was fitted on the 6-monthly orthoptic measurements of angle and refraction in the ELISSS that antedated surgery, loss to follow-up, or final examination. In the random-effects model (see online-only supplement link or visit, www.simonsz.net), for ELISSS patients the random effect was defined as the deviation of the average angle, the fixed effect. A vector was defined based on age and spherical equivalent of the patient. The variance around the prediction consisted of uncertainty in the estimations, random effects, and residuals.

RESULTS

In the retrospective study, 204 patients who had been first operated between 6 and 23 years previously were eligible. A reoperation had been performed in 32 (19.3%) of the remaining 166 children who were 4.33 SD 1.35 years old at first surgery. The reoperation rate was 7.3% for those with a postoperative angle of -4° to +4° (N = 82), 25% for postoperative divergence > 5°, and 29% for postoperative convergence 10° to 14°. Strabismologists overestimated the reoperation rates at double. In the meta-regression analysis, 12 studies were included. Reoperation rates were between 60% and 80% for children first operated around age 1 and approximately 25% for children operated around age 4 (best fit: -0.221 Ln [age in months] + 1.1069; R(2) = 0.5725). Finally, in the predictions of random-effects model, a small angle at age 1 and hyperopia of approximately +4 increased the chance of spontaneous decrease of the angle into a microstrabismus.

DISCUSSION: The benefit of early surgery for gross binocular vision is balanced by a higher reoperation rate and an occasional child being operated that would have had a spontaneous decrease into a microstrabismus without surgery. The fact that, in the ELISSS, hyperopia was associated with a decrease of the angle underscores the benefit of early refractive correction.