Impact of Myopia on the Utility of the Photopic Negative Response Ratio for Glaucoma Assessment

Background: The objective assessment of visual function is crucial in glaucoma management, highlighting the importance of electroretinography (ERG). This study investigates the diagnostic performance of photopic negative response (PhNR) amplitude and the normalized PhNR/b-wave ratio in diagnosing glaucoma, focusing on the impact of myopia. Methods: Ninety-one glaucoma patients and 19 glaucoma suspects were included, defining myopia as axial length (AL) > 24 mm or > 25 mm. Full-field photopic ERG used a red stimulus on a blue background. Results: Myopic glaucoma patients showed a higher PhNR/b-wave ratio than non-myopic patients (p = 0.023). AL negatively correlated with b-wave amplitude (r = −0.239, p = 0.012). PhNR amplitude demonstrated an area under the receiver operating characteristic curve (AUC) of 0.661 (p = 0.028) overall and was less effective in the myopic subgroup (AUC = 0.574, p = 0.082). The diagnostic performance of the PhNR/b-wave ratio did not achieve statistical significance in either the total group (AUC = 0.616, p = 0.114) or the myopic subgroup (AUC = 0.574, p = 0.332). Conclusions: Standardization using the PhNR/b-wave ratio did not enhance diagnostic accuracy over PhNR amplitude, particularly in myopic patients, underscoring the need for careful interpretation in myopia and further research to optimize electrophysiological diagnostics.