Clinical features in patients with acquired intermittent and constant exotropia who underwent surgery.

Background: acquired exotropia mostly manifests as an intermittent form, and very few cases show constant exotrpia. However, the differences in the clinical features of the constant and intermittent exotropia patients has not been clear yet.

Methods: We retrospectively evaluated 6159 patients with exotropia from 2012 to 2022 in Farabi Eye Hospital, Tehran, Iran. The preoperative data collected were best corrected distance visual acuity (BCVA), spherical equivalent refractive error, amount and laterality of exotropia, presence of amblyopia and anisometropia.

Results: The mean age at the time of surgery was 21.9 ± 13.8 (range, 2-77) years and 3104 (50.4%) cases were male. Constant and intermittent exotropia were observed in 4244 (68.9%) and 1915 (31.1%) cases, respectively. BCVA was significantly worse in the constant than in the intermittent group (P < .05). In cases with dominancy, the non-dominant eye in intermittent exotropia patients showed significantly more minus spherical equivalent (-1.28 ± 3.03 diopter) compared to the constant group (-0.63 ± 4.41 diopter) (P < .001). Moreover, the mean angle of horizontal and vertical deviation at distance and near in patients with constant exotropia was significantly higher than in the intermittent cases, either when there was a dominance in one eye or in cases with no dominance (P < .001). Amblyopia was found in 38.3% of cases with constant and 13.1% with intermittent exotropia (P < .001). Anisometropia was observed in 821 (19.34%) with constant and 88 (4.6%) with intermittent exotropia (P < .001).

Conclusion: Constant exotropic patients had worse BCVA, larger angle of deviation, and higher prevalence of amblyopia and anisometropia compared to the intermittent cases.