Factors influencing the success of patch therapy in patients with intermittent exotropia: a retrospective case-control study

Abstract Background Part-time occlusion is used to delay or avoid surgery in intermittent exotropia; however, the treatment criteria and optimal duration remain unclear. This retrospective case-control study aimed to identify factors influencing deviation angle normalization and recurrence risk after patch therapy in intermittent exotropia. Methods Patients with intermittent exotropia who underwent 2–4-hours patching were divided into treatment success and failure groups; the treatment success group was divided into recurring and non-recurring subgroups. Patients whose deviation angle recovered to 10 prism diopters (PD) or under were seen as treatment success, patients whose deviation angle went 15 PD or more in the 1 year follow up after treatment success was achieved were seen as recurring group. Visual acuity, refraction, deviation angle, control, stereoacuity, patching time, and duration were investigated. The main outcomes included characteristics of patients whose deviation angle normalized. The independent t-test and chi-square test were used to compare continuous and categorical variables, respectively. Shapiro-Wilk normality testing was conducted before analyses. Cox regression analysis was used to compare the treatment success and treatment failure groups. Logistic regression analysis was used to compare the recurring and non-recurring subgroups within the treatment success group. Kaplan–Meier survival analysis was performed to calculate the probability of treatment success, and the log-rank test was used to compare the patching duration between the treatment failure and success groups. Results Among the 59 patients included, 30 required surgeries due to treatment failure. Eleven of 29 patients in the treatment success group experienced recurrence. The deviation angle normalized within an average of 494 days in successfully treated patients; it normalized within 331 days in 50% of them. The treatment failure group had a larger initial deviation angle (p ≤ .0001). Shorter patching duration was a predictive factor for treatment success (p = .002). However, no significant factors were found between recurring and non-recurring cases. Conclusions Patch duration and good compliance, especially considering age, are key factors in treatment success.