Relationship between structural and functional changes in glaucomatous eyes: a multifocal electroretinogram study

Abstract

Background The nasal to temporal amplitudes ratio (N/T) of multifocal electroretinography (mfERG) scans measured within 5° of the macula can be used to detect glaucomatous change. The photopic negative response (PhNR) of mfERG elicited by a circular stimulus centered on the fovea was significantly reduced in eyes with glaucoma. The PhNR to B-wave ratio (PhNR/B) is the optimal measure of the PhNR. However, clinical superiority for evaluating glaucoma patients has not been determined between N/T and PhNR/B yet. Methods For morphological assessments, ganglion cell complex (GCC) in six regions and the average were measured by optical coherence tomography (OCT). For functional assessment, Humphrey visual fields (VF) with mean sensitivities (MT) and mfERG scans with parameters of N/T and the multifocal photopic negative response to B-wave ratio (mfPhNR/B) were measured. Sixty-nine eyes of 44 glaucoma patients were included and correlations between mfERG parameters and OCT or VF parameters were evaluated. Results The mean age of patients was 59.4 years. The mean deviation for all eyes obtained with the VF 30–2 and VF 10–2 was − 7.00 and − 6.31 dB, respectively. Significant correlations between GCC thickness or VF parameter and the N/T were found, especially in the inferior and inforotemporal retinal areas corresponding to superior and superonasal VF sectors (GCC vs N/T; coefficient = − 7.916 and − 7.857, and MT vs N/T; coefficient = − 4.302 and − 4.437, in the inferior and inforotemporal retinal areas, respectively, all p values < 0.05). However, similar associations were not obtained between mfPhNR/B and OCT or VF parameters. The mfPhNR/B only in the inferotemporal sector was significantly correlated with the average thickness of GCC (coefficient = 4.823, P = 0.012). Conclusions The N/T was correlated with GCC and VF in more numbers of measurement areas than the mfPhNR/B in the current study, however, a future study modifying the stimuli and amplitudes to obtain the spatial correspondence to OCT and VF measurement will be required to evaluate the value of mfERG.

Use of multifocal electroretinograms to determine stage of glaucoma

“…The amplitudes of the first positive peak, P1 and the second positive peak, P2 were studied ( Fig 2A ). The amplitudes of P1 and P2 of the first slice of the second order kernel was measured according to a published method [ 13 , 18 ].…”

“…However, when a comparison was made between the temporal and nasal hemifields within the central 5° radius, there was a statistically significant difference in the nasal-temporal (N/T) P1 amplitude ratio between normal eyes and glaucoma patients, and there was a significant increase of the P1 amplitude and a nasal-temporal asymmetry was lost in the glaucoma patients [ 12 ] as had been reported [ 13 – 17 ]. Thereafter, significant correlations were found between the ganglion cell complex (GCC) thickness, the mean sensitivities and the N/T P1 amplitude ratio, especially in the inferior and inferotemporal retinal areas (corresponding to superior and superonasal visual field) [ 18 ]. These findings indicated that the mfERGs might be helpful in determining the functional defects in glaucomatous eyes.…”