Ethnic differences in optic nerve head and retinal nerve fibre layer thickness parameters in children

Aim To examine ethnic differences in optic nerve head and retinal nerve fibre layer (RNFL) parameters between European Caucasian and East Asian children aged 6-12 years. Methods Of 4118 children examined in the Sydney Childhood Eye Study (incorporating the Sydney Myopia Study) from 34 randomly selected primary and 21 secondary schools during 2003-5, 3382 (82.1%) had optical coherence tomography (OCT; Zeiss Stratus) data suitable for analysis. 'Fast' optic disc and RNFL scans were used. Ethnicity was defined only when both parents were of the same ethnicity. Results East Asian children tended to have a lower birth weight, were shorter with a smaller body mass index and were less hyperopic than European Caucasian children of the same age. After adjusting for age, gender, axial length, birth weight and optic-disc area, East Asian children had similar mean vertical disc diameters to European Caucasians (p=0.38, p=0.64 for 6-12 years, respectively) but 30-43% larger mean vertical cup diameters (p<0.0001 for both), resulting in larger mean cup/disc ratios (p<0.0001 for both). Compared with European Caucasians (101.95 mm and 104.57 mm, respectively), East Asian children had thicker mean average RNFL (105.45 mm and 107.92 mm, respectively; p=0.0006 and 0.0001) and thicker non-nasal RNFL quadrants in both ages. Conclusions Compared with European Caucasian children, East Asian children generally had thicker RNFL and larger mean cup/disc ratios. Given the relatively lower prevalence of open angle glaucoma in Asians, these anatomical variations could contribute to better understanding of apparent racial differences in glaucoma susceptibility.