Abstract
Purpose :
Substantial loss of retinal ganglion cells (RGC) has been shown in perimetric glaucoma and empirical estimates of RGC count combining structural and functional test results were found to significantly correlate with the histological reports.in early glaucoma. The purpose was to determine whether estimated RGC count mediated the relationships among steady-state pattern electroretinography (ssPERG) and optical coherence tomography (OCT) thickness measures in glaucoma suspects (GS).
Methods :
In this prospective cross-sectional study, 10 GS subjects (20 eyes) were recruited at the Manhattan Eye, Ear, and Throat Hospital, with normal Humphrey visual field tests with 24-2 MD better than -2dB, and suspicious optic nerves. Subjects underwent complete eye examinations, OCT, standard automated perimetry (SAP), and ssPERG testing. Two groups of 10 eyes in each, were created based upon clinical data: healthy subjects and GS. RGC counts were estimated using the combined structure-function index (CSFI). We performed mediation analyses with each ssPERG parameter (Magnitude, MagnitudeD and Mag/MagD ratio) as independent variables (X), estimated RGC count as the mediator (M), and average retinal nerve fiber layer thickness (AvRNFLT), mean deviation (24-2 MD), and average ganglion cell layer and inner plexiform layer thickness (AvGCIPLT) as the dependent variables (Y), for a total of nine analyses. For each analysis, the significance of the indirect and direct effects of X on Y were determined using 5,000 bootstrapped samples with a 95% confidence interval (CI).
Results :
Estimated RGC count, AvRNFLT, 24-2 MD, and AvGCIPLT were reduced in GS (p < 0.015 for all parameters). Pearson and partial (age-adjusted) correlations revealed that all ssPERG parameters correlated with ARNFLT (r > 0.51, p < 0.027). MagnitudeD/Magnitude (MagD/Mag) ratio correlated with average GCIPLT (r = 0.47, p = 0.042). Nine mediation analyses revealed that estimated RGC count mediated the relationships among ssPERG parameters, ARNFLT, and average GCIPLT.
Conclusions :
Estimated RGC count mediates the relationships between ssPERG parameters and OCT thickness measures in GS, underlying the importance of addressing the RGC dysfunction as early as possible to prevent future structural damage and RGC apoptosis.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.