A Combined Index of Steady-State Pattern Electroretinogram and Optical Coherence Tomography Improved the Detection of Early Glaucoma

Introduction: The aims of the study were to evaluate the structure-function relationship between steady-state pattern electroretinogram (ssPERG), optical coherence tomography (OCT), and visual field (VF) tests and to investigate indicators that enhance the detection of preperimetric and early-stage primary open-angle glaucoma (POAG). Methods: In this retrospective cohort study, patients with POAG and normal subjects who underwent ssPERG, OCT, and VF tests were included. We defined the ratio of the amplitudes from 0.8° checks to 16° checks as the pattern electroretinogram ratio (PERGratio). The thickness of themacular ganglion cell inner plexiform layer and the circumpapillary retinal nerve fiber layer (cpRNFL) were measured using spectral-domain OCT. We compared the areas under the receiver operating characteristic curves (AUCs) for ssPERG, OCT, and VF test parameters. A combined index using structural and functionalmeasures was generated using logistic regression models to improve diagnostic accuracy. Results: Four parameters had AUCs higher than 0.8; PERGratio (AUC = 0.890), average cpRNFL thickness (AUC = 0.827), 7 o'clock cpRNFL thickness (AUC = 0.844), and inferior quadrant cpRNFL thickness (AUC = 0.830). The new index, which combines the PERGratio and 7 o'clock cpRNFL thickness, significantly improved diagnostic accuracy (AUC = 0.951), outperforming the best four parameters (all p = 0.004). Furthermore, the combined index of PERGratio and 7 o'clock cpRNFL thickness showed significantly higher diagnostic accuracy compared to those combining the 7 o'clock cpRNFL thickness with VF mean deviation, pattern standard deviation, and VF index. Conclusion: The combined index of ssPERG, indicative of retinal ganglion cell dysfunction, and the OCT test, indicative of focal structural damage, improved the detection of patients with POAG in its early stage.