New Combined Structure-Function Models for Estimating Retinal Ganglion Cell Count in Glaucoma Subjects using Steady-State Pattern Electroretinography.

Abstract

Purpose : To estimate retinal ganglion cell (RGC) count in preperimetric and early glaucoma eyes using optical coherence tomography (OCT) and steady-state pattern electroretinography (ssPERG) parameters.

Methods : In this prospective cross-sectional study, 25 subjects (50 eyes) were recruited at the Manhattan Eye, Ear, and Throat Hospital. Subjects underwent complete eye examinations, OCT, standard automated perimetry (SAP), and ssPERG testing. Eyes were divided into three groups based on clinical data: control (N= 30), preperimetric (N = 14), and early glaucoma (N = 6) eyes. The combined structure-function index (CSFI), which estimates retinal ganglion cell count from SAP and OCT parameters, was calculated in each study subject. Two prediction models were then derived using a step-wise linear regression to predict the CSFI from ssPERG parameters, age, and ARNFLT in 30 eyes selected at random (training sample). The prediction models were then validated using cross-validation with the remaining 20 eyes in our cohort (validation sample).

Results : Average retinal nerve fiber layer thickness (ARNFLT) and all ssPERG parameters were significantly different among groups (ANOVA p < 0.001). In each study group, ARNFLT and ssPERG parameters correlated with the CSFI (r² ≥ 0.31, p < 0.001). In our training sample (N = 30), two step-wise linear regression models using ssPERG parameters magnitude (Mag) and magnitudeD (MagD), ARNFLT, and age resulted in significant equations (F(3,26) ≥ 63.00, R² ≥ 0.88, p < 0.001). The standard error of the estimate (SE) (SE ≤ 69,771.65) for each model corresponded to a small relative standard error (RSE) ≤ 7.20%. Applying the equations of each model to the validation sample (N = 20) resulted in similar metrics (R² ≥ 0.91, SE ≤ 60,917.46, RSE ≤ 6.29%). ANOVA Games-Howell Post-Hoc analysis demonstrated that study groups exhibited more significant differences in RGC estimates than individual ssPERG and OCT measurements.

Conclusions : ssPERG parameters can be combined with OCT measurements to estimate RGC count in preperimetric and early glaucoma eyes, accounting for > 88% of variance from RGC counts estimated with the CSFI. These new combined structure-function models can distinguish preperimetric eyes from early glaucoma eyes.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.