Reduced Photoreceptor Outer Segment Layer Thickness and Association with Vision in Amblyopic Children and Adolescents with Unilateral High Myopia

Purpose: To quantitatively compare reflectivity and other morphological changes of the photoreceptors of normal eyes with amblyopic eyes using the longitudinal reflectance profile (LRP) on swept-source optical coherence tomography (SS-OCT) images in children and adolescents with unilateral high myopia. The relationships between OCT parameters and visual acuity were investigated.

Method: Twenty-six amblyopes with unilateral high myopia and 34 age-, axial length- and spherical equivalent-matched normal controls were recruited. All participants underwent SS-OCT and detailed ophthalmic investigations. The reflectivity of the outer retinal and photoreceptor outer segment layer thickness were quantified by LRP using ImageJ software. All parameters were measured at three selected regions: at the fovea, 1 mm nasal to the fovea and 1 mm temporal to the fovea. Differences between the groups were evaluated.

Results: The mean choroidal thickness was thinner in amblyopic eyes compared with controls (165.19 ± 59.02 μm vs 214.97 ± 66.41 μm at the fovea; 128.77 ± 57.06 μm vs 161.54 ± 57.37 μm at 1 mm nasal to the fovea; 188.13 ± 59.51 μm vs 219.87 ± 61.78 μm at 1 mm temporal to the fovea, P < .05). The amblyopic eyes had higher reflectivity of the ellipsoid zone at 1 mm nasal to the fovea only (85.41 ± 25.78 vs 70.76 ± 18.69, P = .02). The mean length of the photoreceptor outer segment (OS) layer was significantly greater in the control eyes than in the amblyopic eyes at all three regions (20.19 ± 1.89 vs 18.70 ± 2.23 at the fovea, P = .006; 16.06 ± 1.47 vs 15.07 ± 1.30 at 1 mm nasal to the fovea, P = .008; 15.81 ± 1.58 vs 14.56 ± 1.87 at 1 mm temporal to the fovea, P = .006). The shortened OS length was associated with poorer visual acuity.

Conclusion: The results of this study revealed that the amblyopes with unilateral high myopia had thinner choroidal thickness and shortened OS thickness compared to normal controls. The findings indicate that abnormal anatomic changes in the amblyopic children and adolescents with unilateral high myopia were not only due to high myopia but more likely due to a combination of high myopia and amblyopia.