Abstract
Purpose :
To study the slope of the retinal nerve fiber layer thickness (RNFL-t) along retinal nerve fiber bundles (RNFBs) as a measure of correlating retinal ganglion cell axons with standard automated perimetry in healthy and early glaucoma eyes utilizing polarization-sensitive OCT (PS-OCT).
Methods :
This is a cross-sectional study where we extracted virtual B-scans along RNFBs from stitched wide-field PS-OCT data sets of 38 early glaucoma and 9 healthy eyes. Trajectories of the RNFBs were traced from the 24-2 and 10-2 visual field (VF) test points to the optic disc (OD) using the Schwarzhans et al. (PMID: 35154854) RNFB tracing method. The RNFL-t slope was calculated by a linear fit of a 1mm long segment of the virtual B-scan centered on the corresponding VF point. All patients underwent two 24-2 and two 10-2 visual tests. Threshold values of the four VF tests were merged and averaged per patient. Spearman correlation coefficients were calculated between the VF threshold values and corresponding RNFL-t slopes. Data of left eyes were inverted to right eyes for calculation of group averages. Data are presented in retina view.
Results :
The averaged VF mean deviation was -2.87±1.85 dB in glaucoma and -0.35±0.96 dB in healthy eyes. The mean RNFL-t slope was less steep in glaucoma eyes compared to healthy (glaucoma: -8±17 vs. healthy: -12±22 μm/mm, p<0.001). Figure 1 shows averaged maps (healthy and glaucoma combined) of VF threshold values (A), RNFL-t slope (B), and a correlation map in (C). VF defects were mainly observed in the paracentral superior hemisphere and in the nasal inferior visual field. The steepest RNFL-t slopes were observed near the OD, while they were close to zero on the more peripheral VF points and near the temporal raphe. The strongest correlations between RNFL-t slopes and VF sensitivity were observed in the paracentral inferior retina, reaching moderate correlation of up to r=-0.62.
Conclusions :
We found a moderate correlation between visual field sensitivities and the RNFL-t slope in areas with visual field defects. As a novel biomarker, RNFL-t slope could offer insights into focal glaucoma damage and the prediction of VF sensitivity loss. Further research with larger patient cohorts and more sophisticated analytical techniques is needed to fully assess the utility of this biomarker.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.