Abstract
Purpose :
The interchangeability of using different peripapillary retinal nerve fibre layer (RNFL) ring sizes in assessing rates of change is unclear. In this study we compared rates of change and longitudinal variability between three OCT RNFL ring sizes (3.5, 4.1, 4.7mm) in a cohort of healthy and glaucomatous eyes
Methods :
Retrospective analysis of 209 eyes of 107 patients who underwent peripapillary RNFL scans on ≥four consecutive follow up visits. Scans were taken using the Spectralis® OCT (Heidelberg Engineering, Heidelberg, Germany). We calculated the rate of change (ROC) of global thickness (GT) and sectoral thickness [Supero-nasal (SN), Supero-temporal (ST), Infero-nasal (IN), Infero-temporal (IT)] values in the three ring sizes using linear mixed-effect models. Regression residuals were used as a measure of variability for each ring size
Results :
44.9% subjects were male with mean age of 67.3 years. Most eyes had manifest or suspected glaucoma (69.6%) and 79.4% were phakic. Baseline mean pinhole visual acuity, global RNFL thickness and mean deviation (MD) was 0.13logMAR (SD -0.26), 67.1um (13.8), and -2.8dB (3.7). Mean follow up period was 2.41 years. GT ROC was highest for the 3.5mm ring (-0.53um/year) compared to 4.1 and 4.7mm (-0.47, -0.36um, p=0.20). SN ROC was greatest in the 3.5mm ring (-0.81um/year) compared to 4.1 and 4.7mm (-0.57, -0.28, p<0.001). The ST and IN sectors consistently showed higher ROC across all ring sizes. ROC in the inferior sectors (IN, IT) was significantly higher in the 3.5 (-1.10, -0.74) and 4.1mm rings (-0.95, -0.56) compared to 4.7mm (-0.76, p<0.001 & -0.34, p<0.002). The 4.1mm ring had the greatest proportion of patients with significant RNFL progression as defined by p-value < 0.05 (20.4%), followed by 3.5 (17.4%) and 4.7mm (16.3%). GT MAR was similar for 3.5, 4.1 and 4.7mm ring sizes (1.54, 1.62 and 2.24um, p=0.83). There was no significant difference in MAR when comparing rings by individual sectors (SN p=0.28, ST/IN/IT, p=0.19). We found GT provided lower MAR than individual sectors
Conclusions :
While global RNFL rates of change were similar across the 3.5, 4.1 and 4.7mm ring sizes, this differed significantly in sector thickness values. Though there is no difference in longitudinal variability, clinicians should use a consistent ring size to monitor glaucoma patients, as observed rates of change may vary based on ring size and sector.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.