Abstract
Purpose :
Investigate and evaluate nerve fiber layer (NFL) reflectance normalized by different references for repeatability and reproducibility.
Methods :
In this cross-sectional observational study, glaucoma patients had disc rim thinning or the nerve fiber layer defect confirmed on stereo photography, with or without perimetric defect. Normal eyes had normal eye examination, including disc and perimetry. Participants were scanned with a cubic 6x6 mm disc scan using spectral-domain OCT. We normalized the OCT intensity inside the NFL either by the average of pixels in a reference band or all pixels below (equivalent to attenuation coefficient), then summed the normalized value inside the NFL for each a-scan. Finally we averaged the NFL reflectance in the peripiallary area. We selected several reference bands: retinal pigment complex (RPC), the band between NFL and Bruch’s membrane (Post-NFL), and between inner Nuclear Layer (INL) and Bruch’s membrane (Post-INL). The within-visit repeatability and between-visit reproducibility of these metrics (NFL/RPC, NFL/Post-INL, NFL/Post-NFL, and NFL/AC) were compared for normal and glaucoma eyes. Pooled standard deviation and Intra-Class Correlation (ICC) were used to evaluate the performance.
Results :
A total of 77 eyes (55 glaucoma and 22 healthy) were acquired from 77 participants. Each eye had two scans on the same day for within-visit analysis. The duration between two scans for between-visit analysis was 5 months to 14 months. The average age was 64±10 years for glaucoma and 58±10 years for normal participants. Females were 59%. For within-visit repeatability, NFL/Post-INL had the best value in both normal and glaucoma eyes, followed by NFL/post-NFL, NFL/AC, NFL/RPC (Table 1). For between-visit reproducibility, NFL/Post-INL was the best in glaucoma eyes, but NFL/AC was the best in normal eyes. NFL/Post-INL was significantly better than NFL/RPC in glaucoma eye for both within-visit repeatability and between-visit reproducibility (p<0.04).
Conclusions :
NFL reflectance, normalized by the average between INL and Bruch’s membrane, showed better repeatability and reproducibility than other references, especially RPC. However, the summation of attenuation coefficients showed a smaller difference between within-visit repeatability and between-visit reproducibility than others.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.