Intermittent exotropia: relation between age and surgical outcome: a change-point analysis

To study the relationship between age and response to surgery in patients with intermittent exotropia and to identify change points in response to surgery.

A retrospective analysis was conducted on 311 patients with intermittent exotropia who had bilateral lateral rectus recession using standard tables with minimum follow-up of 6 months. Data were analyzed using the change-point analysis software to identify cutoff points. A prospective pilot study was then performed on 171 consecutive patients with intermittent exotropia with the same clinical characteristics, in whom amount of recession was modified according to the identified cutoff points. In angles with two change points, 1-mm recession was reduced from patients younger than the lower change point and 1.5-mm recession was added to those older than the upper change point. In angles with one change point, 1.5-mm recession was added to those older than the change point. Satisfactory alignment was defined as esophoria/tropia ≤ 5Δ to exophoria/tropia ≤ 8Δ.

There was a negative correlation (P<0.01) between response to surgery and age at surgery for all angles. In younger patients (<7 years) in whom surgical dose was reduced, there was no significant change in success rate (77%), compared with those who had surgery using standard tables (75%). In older patients (>12 years) in whom surgical dose was increased, there was a statistically significant increase in success rate (80% vs 41%).

Modifying the surgical dose according to age can improve the success in patients with intermittent exotropia.