Evaluating the Impact of Interocular Suppression on Retinal Microvasculature in Intermittent Exotropia by Optical Coherence Tomography Angiography.

PURPOSE: To evaluate retinal microvascular alterations in patients with intermittent exotropia (IXT) using optical coherence tomography angiography (OCTA), with particular emphasis on differences between suppressed and non-suppressed eyes and their relationship with deviation magnitude. MATERIALS AND METHODS: In this prospective observational study, patients with IXT and age and sex matched healthy controls underwent macular OCTA imaging. Vessel densities of the superficial (SCP) and deep capillary plexuses (DCP), as well as the foveal avascular zone (FAZ) area, were quantified and analyzed across four quadrants (superior, inferior, nasal, and temporal). Intergroup comparisons were performed among suppressed, non-suppressed, and control eyes, and subgroup analyses were conducted based on deviation magnitude (<40 and ≥40 prism diopters). RESULTS: Among 57 patients with intermittent exotropia (114 eyes) and 57 healthy controls (57 eyes), no significant differences were found in SCP vessel densities across groups (p > 0.05). In contrast, DCP vessel density was significantly higher in the nasal (p = 0.001) and superior (p = 0.015) quadrants of both suppressed and non-suppressed eyes compared with controls, with no interocular differences between the two eye groups. The FAZ area likewise showed no significant variation among groups (p = 0.776). Subgroup analysis demonstrated that the increase in nasal DCP vessel density persisted in both small to moderate (<40 prism diopters) and large angle (≥40 prism diopters) exotropia. CONCLUSIONS: Patients with IXT exhibited quadrant-specific increases in DCP vessel density in both suppressed and non-suppressed eyes compared with healthy controls, whereas SCP vessel density and FAZ area remained unchanged. The absence of interocular differences in DCP vessel density suggests that the observed retinal microvascular alterations are associated with IXT regardless of suppression status.