Establishing normal interocular symmetry range for macular optical coherence tomography parameters in healthy children

The study aimed to evaluate the interocular symmetry of macular sublayer thickness among healthy children aged 6-12 years. The Shiraz Pediatric Eye Study included 500 randomly selected children who underwent SD-OCT of the macula and optical biometry using the IOLMaster-500. Exclusion criteria involved ocular abnormalities or axial lengths outside the 21.5-26.5 mm range. Software recorded total retinal thickness and sublayer thickness within each ETDRS subfield. The study included 862 eyes from 431 healthy children, with 254 girls (59%). The anticipated variation in total retinal thickness between eyes was below 13 µm in the fovea and under 7 µm in the inner or outer ring for 95% of the population. For nerve fiber layer and inner plexiform layer, the expected variation ranged from 2 to 4 µm, and for the ganglion-cell layer, it ranged from 2.5 to 5 µm. Intraclass correlation coefficient (ICC) rankings for retinal topography were highest in the outer ring, followed by the inner ring and fovea. The highest ICC for individual layers was found in overall retinal thickness, followed by inner retinal layers, outer-nuclear layer, inner plexiform layer, and inner nuclear layer. The study establishes a reliable reference range for interocular variances in macular sublayers, aiding clinical decision-making. The outer ring (3-6 mm) is most dependable for analysing most sublayers, while the inner ring is most suitable for examining the ganglion-cell layer.