Interocular differences in subfoveal choroidal thickness in monocular intermittent exotropia

PURPOSE To determine whether subfoveal choroidal thickness and central foveal thickness differ according to the presence of fixation preference in patients with intermittent exotropia without anisometropia or amblyopia. METHODS Children >= 4 years of age with either monocular (fixation preference) or alternating intermittent exotropia on three consecutive visits who had no anisometropia, no amblyopia, and spherical equivalent of +/- 1.25 D or less in both eyes were recruited for this study. Subfoveal choroidal thickness and central foveal thickness, measured using spectral domain optical coherence tomography, in the monocular group and the alternating group were compared. RESULTS A total of 81 patients were enrolled: 46 in the monocular exotropia group and 35 in the alternating exotropia group. The interocular difference in subfoveal choroidal thickness was -11.0 +/- 18.0 mm in the monocular group (dominant eye - nondominant eye) and 1.9 +/- 22.2 mm in the alternating group (right eye - left eye). The difference between groups was statistically significant (P = 0.005). The interocular difference in central foveal thickness was 1.1 +/- 5.7 mmin the monocular group (dominant eye - nondominant eye) and 0.9 +/- 5.0 mm in the alternating group (right eye - left eye). The difference between groups was not significant. CONCLUSIONS In patients with intermittent exotropia without amblyopia, the difference in subfoveal choroidal thickness between the eyes in the monocular group was significantly greater than that between eyes in the alternating group. These findings suggest the presence or absence of fixation preference may affect subfoveal choroidal thickness.