Assessment of Peripapillary Retinal Nerve Fiber Layer Optical Density Ratios in Healthy Eyes Using Optical Coherence Tomography with Different Analytical Radii

Abstract

Purpose To explore the characteristics and determinants of peripapillary retinal nerve fiber layer (RNFL) optical density (OD) by optical coherence tomography (OCT) in healthy eyes with varied analytical radii. Methods Peripapillary OCT scans centered at the optic disc of 150 eyes from 150 healthy subjects (64 males and 86 females) were included. Under 5 analytical circles with different radii (1.45 mm, 1.7 mm, 1.95 mm, 2.2 mm and 2.45 mm), the circumpapillary circular cross-sectional images were exported for further analysis using Image J. Peripapillary RNFL and retinal pigment epithelium (RPE) OD in different quadrants and clock-hours were obtained. RNFL optical density ratio (ODR) was then calculated as RNFL OD divided by RPE OD. A linear mixed-effects model analysis was performed to assess the relationship between RNFL ODR and analytical radius, accounting for axial length, age, spherical equivalent, thickness and image score. Results The RNFL ODRs had a double-hump pattern with peaks in the superior and inferior quadrants and troughs in the temporal and nasal areas. In the linear mixed-effects model analysis, a trend of decreasing mean RNFL ODR with increasing analytical radius was found (0.9227 ± 0.0689, 0.9063 ± 0.0620, 0.8916 ± 0.0552, 0.8729 ± 0.0553 and 0.8575 ± 0.0564 respectively, p = 0.034). RNFL ODR values was negatively correlated with age (p < 0.001), positively correlated with corresponding RNFL thickness (p < 0.001). No significant correlation was found between RFNL ODR and image score, axial length and spherical equivalent. Conclusions RNFL ODR profile showed a comparable double-hump configuration with RNFL thickness. RNFL ODR values tended to decrease with larger analytical circles and older age, and increase with corresponding RNFL thickness. These factors should be considered when interpreting RNFL ODR in glaucoma assessment.