Comparison between broadband and monochromatic photopic negative response in full-field electroretinogram in controls and subjects with primary open-angle glaucoma.

PURPOSE: A prospective, cross-sectional, case-control study was conducted to investigate the role of broadband and monochromatic photopic negative response (PhNR) of the full-field flash electroretinogram (ERG) in the evaluation of ganglion cell damage in primary open-angle glaucoma (POAG) subjects.

METHODS: Subjects with POAG and age-matched normal subjects were recruited from the outpatient department of a tertiary eye care center in South India. A total of 25 patients with POAG and 50 age-matched normal subjects were recruited. ERG was recorded using broadband (3.5 cd.s/m2 white stimulus on 10 cd/m2 white background) and monochromatic (3.5 cd.s/m2 red stimulus on 10 cd/m2 blue background and 1 cd.s/m2 blue stimulus on 10 cd/m2 yellow background) stimuli.

RESULTS: The reduction in PhNR amplitude in POAG compared to normal individuals was higher in red-on-blue PhNR [26.37 µV; p < 0.001, confidence interval (CI) 19.34 to 33.4] as compared to broadband stimuli (16.41 µV; p < 0.001, CI 8.68 to 24.13), and blue on yellow (21.96 µV; p < 0.001, CI 10.12 to 33.8). Red-on-blue PhNR amplitudes correlated better with mean deviation (MD; r = - 0.66, p < 0.05), pattern standard deviation (PSD; r = - 0.4, p = 0.04), visual field index (VFI; r = - 0.58, p < 0.05), and retinal nerve fiber layer thickness (r = - 0.67, p < 0.05) in comparison with broadband and monochromatic blue-on-yellow PhNR. Receiver operating characteristic curve revealed largest area under the curve (0.89) in red-on-blue PhNR compared to broadband (0.76) and blue on yellow (0.74). The sensitivity and specificity was also higher in red-on-blue PhNR (72% and 80%, respectively) as compared to the other stimuli (sensitivity and specificity of broadband 0.68 and 0.7, blue on yellow 0.64 and 0.7, respectively).

CONCLUSION: Correlation of PhNR with Humphrey visual field parameters and retinal nerve fiber layer thickness showed that red-on-blue PhNR can be a useful additional tool for clinical assessment of retinal ganglion cell dysfunction in glaucoma patients. Red-on-blue PhNR was more sensitive as compared to white-on-white and blue-on-yellow PhNR in identifying ganglion cell dysfunction and correlates well with other structural and functional tests for glaucoma such as MD, PSD, VFI, and RNFL thickness.