Macular microvasculature in unilateral amblyopia: a paired-eye optical coherence tomography angiography comparison of anisometropic and strabismic subtypes.

BACKGROUND: Amblyopia is a functional decrease in visual acuity in infancy or early childhood that occurs with abnormal binocular interaction during a critical stage of visual cortex neurodevelopment. This study assessed optical coherence tomography angiography (OCTA) parameters in amblyopic eyes compared to non-amblyopic fellow eyes. METHODS: In this case-control study, 46 eyes from 23 patients aged 5 to 14 years with unilateral amblyopia were examined. Non-amblyopic eyes of the same patient were included as internal controls. All participants were imaged by OCTA to assess superficial and deep vascular structure of the macula, central macular thickness, foveal avascular zone (FAZ) area, and acircularity index. Linear mixed-effects regression with random intercept per patient was used, with results unadjusted and adjusted for axial length. RESULTS: Deep capillary plexus (DCP) temporal density was 3.16 percentage points lower in amblyopic than fellow eyes (95% CI: -6.20 to -0.12, nominal p=0.04), but this difference did not survive correction for multiple testing (Benjamini-Hochberg q=1.00). After false discovery rate adjustment no OCTA parameter differed significantly. In exploratory subtype-stratified analysis the amblyopic-versus-fellow effect did not differ between anisometropic and strabismic subtypes (interaction p=0.61). CONCLUSION: After adjustment for axial length and correction for multiple testing, no macular microvascular parameter differed between amblyopic and fellow eyes; the nominal reduction in DCP temporal density is hypothesis-generating only. Because the fellow eye is not a normal eye, these findings exclude a clinically appreciable inter-ocular difference but cannot exclude a bilateral microvascular effect of amblyopia, which requires larger cohorts including age-matched healthy controls.