Comparing focal and global responses on multifocal electroretinogram with retinal nerve fibre layer thickness by spectral domain optical coherence tomography in glaucoma.

PURPOSE: To evaluate first and second order responses on multifocal electroretinogram (mfERG) and with retinal nerve fibre layer thickness (RNFL) on Cirrus spectral domain optical coherence tomography (SD-OCT) in glaucoma.

METHODS

Patients (old and new) diagnosed with primary open angle glaucoma, primary angle closure glaucoma or normal tension glaucoma attending glaucoma services from November 2012 to January 2013 were screened. Ninety-seven eyes fulfilling inclusion criteria were evaluated by Humphrey visual field, Cirrus SD-OCT imaging and mfERG (Veris Science 5.1.10X; EDI, Redwood City, California, USA) for this observational cross-sectional study. The global and averaged quadrant-wise peak-to-trough amplitudes and peak implicit times of the first trough (N1), the first peak (P1) and the second trough (N2) of the mfERG were compared with average RNFL-full circle (FC) or quadrant RNFL thickness in early (mean deviation (MD) >-6 dB), moderate (MD -6 to -12 dB) and advanced glaucoma (MD <-12 dB).

RESULTS

The RNFL-FC correlated with P1N2 amplitude on univariate analysis (r=0.7, p=0.004) and N2 amplitude (r=-0.4, p<0.001). Comparing relationships in different stages of glaucoma, P1N2 amplitude correlated significantly with RNFL-FC and superotemporal quadrant, RNFL-superior temporal (ST), in early and moderate glaucoma only. In contrast, the implicit time of P1N2 correlated significantly with RNFL-FC and RNFL-ST only in severe glaucoma while in earlier stages, this relationship did not hold true. On multivariate analysis, P1N2 amplitude correlated with age (β=-0.2, p<0.001), RNFL-FC (β=0.05, p=0.05), RNFL-ST (β=0.06, p=0.01) and cup-disc ratio (β=-3.2, p=0.006).

CONCLUSIONS

Of all responses on mfERG, P1N2 amplitude correlates well with RNFL-FC and RNFL-ST on SD-OCT and can be used for monitoring early and moderate glaucoma. Diffuse structural changes may best be reflected by changes in P1N2 implicit time owing to ceiling effect of the amplitude in all regions in severe glaucoma.