Ganglion cell layer segmentation and the two-flash multifocal electroretinogram improve structure function analysis in early glaucoma.

PURPOSE

To improve structure-function analysis in primary open-angle glaucoma (POAG) by including the two-global flash multifocal electroretinogram (2F-mfERG) and macular ganglion cell layer segmentation.

METHODS

Twenty-five glaucoma patients (six pre-perimetric (PPG), 19 POAG) and 16 controls underwent 2F-mfERG, optical coherence tomography (OCT), and standard automated perimetry (SAP). For 2F-mfERG, the root mean square was calculated for the focal flash response at 15-45 ms (DC) and the global flash responses at 45-75 ms (IC1) and 75-105 ms (IC2). For OCT, macular total thickness (mT) and ganglion cell-inner plexiform layer (GCIPL) thickness were analysed. Values from the central 10° and 15° of 2F-mfERG were compared to the corresponding areas from OCT and visual field.

RESULTS

Both PPG and POAG had significantly lower mfERG responses in the central 10° and 15° than the control group. Of the glaucoma patients, 30.7% (three PPG, five POAG) showed central mfERG and GCIPL reduction without a SAP defect in the central 15 degrees. Four patients had a central SAP defect associated with a reduced GCIPL without any detectable dysfunction on mfERG. MfERG DC and IC2 were larger with increased mT (p ≤ 0.02), but GCIPL only related positively to IC2 (p = 0.027). SAP sensitivity also increased with thicker mT but not with GCIPL (p < 0.03 and p = 0.35). DC, IC2, and GCIPL could best differentiate glaucoma from control (AUC values: 0.897, 0.903, and 0.905).

CONCLUSIONS

Structure function analysis in glaucoma can be improved when the GCIPL thickness as well as the 2F-mfERG is included as these measures complement information obtained by SAP.