Interocular amplitude and latency differences of pattern ERG and pattern VEP parameters

DTL versus skin electrodes in recording of multifocal pattern electroretinogram and multifocal photopic negative response

OBJECTIVE

To compare the photopic negative response of the multifocal ERG (mfERGPhNR) and the multifocal pattern electroretinogram (mfPERG) using DTL electrode (EDTL) vs skin electrode (ESKIN) in healthy young and old adults.

METHODS

Ten "Young" [20-27 years] and eight "Old" [60-72 years] participants took part in this study. The electrophysiological responses were recorded binocularly using EDTL and ESKIN. 5-way ANOVAs were applied to investigate the following factors on mfERGPhNR: i) ELECTRODE, ii) DILATATION, iii) AGE, iv) EYE, and v) ECCENTRICITY. For mfPERG, the same factors, except dilatation, were investigated applying 4-way ANOVAs. These were conducted for amplitude and peak time of different components as well as signal-to-noise-ratio (SNR).

RESULTS

Amplitudes of mfERGPhNR [mfPERG]-based ESKIN recording were reduced to 32-38% [37-38%] compared to EDTL, p < 0.001 . This corresponded to SNR reduction to 80% [60%], p < 0.001 . ESKIN based responses had shorter peak times, by 0.2-0.5 ms for N1 and P1, p < 0.05 , [P1: 1.5 ms, p < 0.001 ]. Both age groups had comparable amplitudes and SNRs, but Young had shorter peak times, by 1.5-2.2 ms for N1 and P1, p < 0.05 [3.7-4.2 ms for N1, P1, N2, p < 0.05 ]. Compared to dilated recordings, undilated mfERGPhNR amplitudes were reduced to 47-87%, p < 0.01 , and peak times were delayed by 2.0-11.8 ms, p < 0.001 .

CONCLUSIONS

mfPERG & mfERGPhNR traces were similar for EDTL and ESKIN. However, for skin electrodes, amplitudes and SNRs were lower and peak times shorter. ESKIN thus seem to be a viable alternative in patients in whom the use of corneal electrodes is precluded, e.g., children and disabled patients, but at the expense of SNR and with reference to ESKIN normative data.

Comparison of functional, structural and vascular characteristics between dominant and nondominant eyes

PURPOSE

The aim of this study was to compare retinal and optic disc functions as well as vascular structures in dominant eyes (DE) and non-dominant eyes (NDE) among healthy adults using pattern electroretinogram (PERG), optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) tests.

METHODS

Seventy-two eyes of 36 healthy subjects with bilateral visual acuity of 1.0 were included. Parameters such as intraocular pressure (IOP), cycloplegic spherical equivalent value (SE), PERG, retinal nerve fiber layer (RNFL) thicknesses and OCTA measurements were evaluated. Ocular dominance was determined using the hole-in-the-card test.

RESULTS

Of the participants, 67% were female, with a median age of 28 (min-max.18-35) years. Right eye dominance was observed in 61.2% of cases, while left eye dominance was seen in 38.8%. There was no significant difference in refractive values between eyes with right and left eye dominance (0.60 ± 0.40 and 0.41 ± 0.28, p = 0.42). The dominant eyes showed significantly higher P50 amplitude (10.2 µV vs. 9.2 µV, p = 0.003) and shorter peak time (47.9 ms. vs. 48.6 ms, p = 0.01) when compared to the nondominant eyes. There were comparable values in the peak times and amplitudes of the N95 component between the dominant and nondominant eyes. The RNFL layer was thicker on average (p, 0.001) as well as in the nasal and inferior quadrants of the dominant eyes (p < 0.05). OCTA analysis revealed no significant differences in the peripapillary and macular capillary vascular densities between dominant and nondominant eyes (p > 0.05), except for the deep whole capillary density in the macula, which was significantly higher in the dominant eyes (p = 0.02).

CONCLUSION

Our results indicate the existence of functional and structural relationships related to ocular dominance. Future studies provide further insights into ocular dominance and its relationship with eye structure.

ISCEV standard pattern reversal VEP development: paediatric reference limits from 649 healthy subjects

PURPOSE

To establish the extent of agreement for ISCEV standard reference pattern reversal VEPs (prVEPs) acquired at three European centres, to determine any effect of sex, and to establish reference intervals from birth to adolescence.

METHODS

PrVEPs were recorded from healthy reference infants and children, aged 2 weeks to 16 years, from three centres using closely matched but non-identical protocols. Amplitudes and peak times were modelled with orthogonal quadratic and sigmoidal curves, respectively, and two-sided limits, 2.5th and 97.5th centiles, estimated using nonlinear quantile Bayesian regression. Data were compared by centre and by sex using median quantile confidence intervals. The 'critical age', i.e. age at which P100 peak time ceased to shorten, was calculated.

RESULTS

Data from the three centres were adequately comparable. Sex differences were not clinically meaningful. The pooled data showed rapid drops in P100 peak time which stabilised by 27 and by 34 weeks for large and small check widths, respectively. Post-critical-age reference limits were 87-115 ms and 96-131 ms for large and small check widths, respectively. Amplitudes varied markedly and reference limits for all ages were 5-57 μV and 3.5-56 μV for large and small check widths, respectively.

CONCLUSIONS

PrVEP reference data could be combined despite some methodology differences within the tolerances of the ISCEV VEP Standard, supporting the clinical benefit of ISCEV Standards. Comparison with historical data is hampered by lack of minimum reporting guidelines. The reference data presented here could be validated or transformed for use elsewhere.

Effect of interocular differences on binocular visual performance after inducing forward scattering

Purpose

To assess binocular visual performance by means of binocular summation on visual function after inducing monocular forward scattering, and to study the influence of interocular differences on ocular parameters.

Methods

Seven young healthy subjects were recruited. Four Bangerter foils and five fog filters were used to induce monocular forward scattering. To analyse the impact of the scatter, visual acuity, contrast sensitivity, visual discrimination capacity and distance stereoacuity were measured binocularly with the filter placed over the dominant eye. Additionally, interocular differences were calculated for four ocular parameters: the Objective Scatter Index (OSI), Strehl ratio (SR), modulation transfer function cut‐off (MTF cut off) and straylight (log[s]). Binocular summation was determined for these visual functions.

Results

A statistically significant deterioration in visual acuity, contrast sensitivity and stereoacuity was seen for all of the filter conditions with respect to the natural state (baseline), with the largest change being recorded for the Bangerter foils. Similarly, the interocular difference for the three retinal image quality parameters (OSI, SR and MTF cut‐off) and log(s) increased significantly for the Bangerter foil condition, but not for the fog filters (except log(s)). Binocular summation declined gradually with the Bangerter foils, but not for the fog filters. Statistically significant correlations were found, that is, the greater the interocular differences, the lower the binocular summation of the visual functions and the greater the distance stereoacuity.

Conclusion

Increased forward scattering in the dominant eye resulted in interocular differences, which reduced the overall binocular visual performance, including the binocular summation of several visual functions and distance stereoacuity. The results suggest that marked interocular differences in ocular parameters should be avoided in cases of ocular pathology, amblyopia and emmetropisation procedures (such as refractive surgery) or a monovision correction for presbyopia.

Further Evidence for the Utility of Electrophysiological Methods for the Detection of Subclinical Stage Retinal and Optic Nerve Involvement in Diabetes

OBJECTIVE

To assess the utility of visual electrophysiological methods, visual evoked potentials (VEPs) and pattern electroretinograms (PERGs) were recorded for the detection of subclinical optic nerve and retinal involvement in patients with diabetes mellitus.

SUBJECTS AND METHODS

The data of 63 patients (126 eyes) with no vascular retinopathy or optic neuropathy were retrospectively analyzed. The patients were divided into polyneuropathic/nonpolyneuropathic groups to differentiate between early and late subclinical stages. The recorded parameters were compared with local reference values.

RESULTS

116 eyes (92%) had VEP and 76 (60%) had PERG abnormalities. The most frequent alteration was latency delay, but waveform and amplitude irregularities were also observed. The simultaneous use of the two methods allowed us to differentiate abnormal VEPs of purely optic nerve origin from those reflecting retinal involvement.

CONCLUSIONS

We suggest that regular electrophysiological screening should receive more attention in the ophthalmological care of diabetic patients.