Purpose: Our aim was to report the characteristics and long-term surgical outcomes of three subgroups of horizontal strabismus in a single institution (divided by strabismus subtype) in a developing country and look into pre-operative factors predictive of surgical success.

Methods: Two hundred and forty-four complete charts of patients, divided into 152 esotropes (ET) and 92 exotropes (XT) who had undergone horizontal strabismus surgeries, were retrospectively reviewed. Charts of patients with muscle palsy, Duane syndrome and consecutive strabismus were excluded; 172 patients were included divided into partially accommodative ET, congenital ET and intermittent XT. Surgical success was defined as a post-operative angle deviation of 12 prism diopters or less.

Results: The mean follow-up period of all patients was 31.64 ± 23.12 months. The subgroups were divided into partially accommodative ET (60 patients), congenital ET (60 patients), and intermittent XT (52 patients). Esotropes (both partially accommodative and congenital) presented earlier (p < 0.001). Also, partially accommodative ET had a significantly higher spherical equivalent (SE) compared to congenital ET patients, who had a higher SE than intermittent XT (p < 0.001). Congenital ET patients had a significantly larger angle of deviation (for both far and near) than both partially accommodative ET and intermittent XT patients (p < 0.001). The overall success rate was 72.67% for the whole group with no significant differences among subgroups. Success rate of partially accommodative ET surgery was 78.33% compared to that of congenital ET at 66.67% and intermittent XT at 73.07%. Significant post-operative improvement in sensory fusion was observed mainly for patients with partially accommodative esotropia and intermittent exotropia.

Conclusion: Our results showed that esotropes (both partially accommodative and congenital) presented earlier, with a higher spherical equivalent in the partially accommodative ET subgroup, while the congenital ET subgroup had the largest angle of deviation for both distance and near. The overall surgical success rate for horizontal strabismus surgery was 72.67% with the 3 subgroups having similar success rates. A younger age at presentation and absence of amblyopia were positively correlated with surgical success in the partially accommodative esotropia group.