Peripapillary Retinal Nerve Fiber Layer Thickness Determined by Spectral-Domain Optical Coherence Tomography in Ophthalmologically Normal Eyes

Objectives: To evaluate the peripapillary distribution of retinal nerve fiber layer thickness (RNFLT) in normal eyes using spectral-domain optical coherence tomography and to study potentially related factors. Methods: In 7 institutes in Japan, RNFLT in 7 concentric peripapillary circles with diameters ranging from 2.2 to 4.0 mm were measured using spectral-domain optical coherence tomography in 251 ophthalmologically normal subjects. Multiple regression analysis for the association of RNFLT with sex, age, axial length, and disc area was performed. Results: Retinal nerve fiber layer thickness decreased linearly from 125 to 89 mu m as the measurement diameter increased (P<.001, mixed linear model). Retinal nerve fiber layer thickness correlated with age in all diameters (partial correlation coefficient [PCC]=-0.40 to -0.32; P<.001) and negatively correlated with disc area in the 2 innermost circles but positively correlated in the 3 outermost circles (PCC=-0.30 to -0.22 and 0.17 to 0.20; P <=.005). Sex and axial length did not correlate with RNFLT (P>.08). The decay slope was smallest in the temporal and largest in the nasal and inferior quadrants (P<.001); positively correlated with disc area (PCC=0.13 to 0.51; P <=.04); and negatively correlated with RNFLT (PCC=-0.51 to -0.15; P <=.01). Conclusions: In normal Japanese eyes, RNFLT significantly correlated with age and disc area, but not with sex or axial length. Retinal nerve fiber layer thickness decreased linearly as the measurement diameter increased. The decay slope of RNFLT was steepest in the nasal and inferior quadrants and steeper in eyes with increased RNFLT or smaller optic discs.