Peripapillary retinal nerve fiber layer thickness in a population of 6-year old children - Findings by optical coherence tomography

Purpose: To study the distribution of retinal nerve fiber layer (RNFL) thickness by ocular and demographic variables in a population-based study of young children. Design: Population-based cross-sectional study. Participants: One thousand seven hundred sixty-five of 2238 (78.9%) eligible 6-year-old children participated in the Sydney Childhood Eye Study between 2003 and 2004. Mean age was 6.7 years (50.9% boys). Methods: Detailed examination included cycloplegic autorefraction and measurement of axial length. Retinal nerve fiber layer scans using an optical coherence tomographer were performed with a circular scan pattern of 3.4-mm diameter. Multivariate analyses were performed to examine the distribution of RNFL parameters with gender, ethnicity, axial length, and refraction. Main Outcome Measures: Peripapillary RNFL thickness and RNFLestimated integral (RNFLEI), which measures the total cross-sectional area of ganglion cell axons converging onto the optic nerve head. Results: Peripapillary RNFL thickness and RNFLEI were normally distributed. The mean +/- standard deviation RNFL average thickness was 103.7 +/- 11.4 mu m and RNFLEI was 1.05 +/- 0.12 mm(2). Retinal nerve fiber layer thickness was least for the temporal quadrant (75.7 +/- 14.7 mu m), followed by the nasal (81.7 +/- 19.6 mu m), inferior (127.8 +/- 20.5 mu m), and superior (129.5 +/- 20.6 mu m) quadrants. Multivariate adjusted RNFL average thickness was marginally greater in boys than in girls (104.7 mu m vs. 103.2 mu m; P = 0.007) and in East Asian than in white children (107.7 mu m vs. 102.7 mu m; P < 0.0001). The RNFL was thinner with greater axial length (P-trend < 0.0001) and less positive spherical equivalent refractions (P-trend = 0.004). Conclusions: Retinal nerve fiber layer average thickness and RNFLEI followed a normal distribution. Retinal nerve fiber layer thickness varied marginally with gender, but differences were more marked between white and East Asian children. Retinal nerve fiber layer thinning was associated with increasing axial length and less positive refractions.