Purpose: The present study was designed to investigate the influence of axial length on macular ganglion cell complex (GCC) thickness and two ratio parameters-the GCC thickness to macular total retinal thickness (G/T) ratio and the GCC thickness to macular outer retinal thickness (G/O) ratio-using spectral-domain optical coherence tomography (OCT).
Methods: In this prospective case series, 74 eyes of 74 healthy Japanese study participants with varying degrees of myopia were recruited. GCC, outer retinal, and total retinal thicknesses were measured with the RTVue-100 system. The G/T and G/O ratios were also calculated. The axial length was determined using the IOLMaster. The correlation between the OCT measurements and axial length was evaluated.
Results: The average axial length was 25.05 ± 1.38 mm. The GCC thickness was significantly correlated with axial length (r = -0.384, P = 0.001). The outer retinal thickness and the total retinal thickness were significantly correlated with axial length (r = -0.444, P < 0.001 and r = -0.493, P < 0.001, respectively), but the G/T and G/O ratios were not (r = -0.093, P = 0.428 and r = -0.091, P = 0.440, respectively).
Conclusions: GCC thickness is affected by axial length. Because the prevalence of myopia is high in Japan, when determining the GCC thickness of Japanese individuals, it seems necessary to consider the axial length as well. To take account of individual variation in axial length, we propose the ratio parameters as a suitable parameter.