Correlation between circumpapillary and macular retinal nerve fiber layer thickness measured by spectral domain optical coherence tomography and multifocal visual evoked potential in patients with primary open-angle glaucoma

Abstract

Purpose This study attempts to examine the relationship between the function of postsynaptic activity of the visual pathway at the level of the striate cortex [multifocal visual evoked potential (mfVEP) responses] and the structural integrity of the retinal nerve fiber layer (RNFL) (by measuring the macular and circumpapillary RNFL thickness). Design This was a prospective nonrandomized interventional clinical study. Patients and methods Patients with controlled primary open-angle glaucoma were included in this study. They underwent complete ophthalmic examination, visual field testing, and macular and peripapillary RNFL thickness measurement by a spectral domain optical coherence tomography (OCT) and mfVEP testing. All similar quadrants on OCT macular and glaucomatous modes were compared with the opposite ones on mfVEP testing (e.g. nasal circumpapillary and macular RNFL thicknesses were compared with the temporal ones on mfVEP testing). Results The mean circumpapillary RNFL thickness showed a significant reduction in each quadrant among the three studied stages of glaucoma ( P l0.001), except the nasal one. The mean macular RNFL thickness showed a significant reduction in the inferior and temporal quadrant among the three stages of glaucoma studied ( P l0.001). The decrease in RNFL thickness in different studied quadrants by OCT correlated positively with the decrease in P1 amplitude ( P l0.0001) and correlated negatively with the increase in P1 latency ( P l0.0001) in the comparable quadrants of the visual field studied by mfVEP. Conclusion The circumpapillary RNFL thickness is a more sensitive detector of glaucoma than the macular one; however, both are affected by glaucoma and can be used for structural evaluation of the RNFL. Both circumpapillary and macular RNFL thickness correlated well with visual field loss detected by mfVEP. mfVEP can be used for functional evaluation and follow-up of the visual pathway of the central 30π of the macula in glaucomatous eyes.