Comparison of isolated-check visual evoked potential and standard automated perimetry in early glaucoma and high-risk ocular hypertension

Preferential Loss of Contrast Decrement Responses in Human Glaucoma

Purpose

The purpose of this study was to determine whether glaucoma in human patients produces preferential damage to OFF visual pathways, as suggested by animal experimental models, patient electroretinogram (ERG), and retinal imaging data.

Methods

Steady-state visual evoked potentials (SSVEPs) were recorded monocularly from 50 patients with glaucoma and 28 age-similar controls in response to equal Weber contrast increments and decrements presented using 2.73 hertz (Hz) sawtooth temporal waveforms.

Results

The eyes of patients with glaucoma were separated into mild (better than -6 decibel [dB] mean deviation; n = 28) and moderate to severe (worse than -6 dB mean deviation, n = 22) groups based on their Humphrey 24-2 visual field measurements. Response amplitudes and phases from the two glaucoma-severity groups were compared to controls at the group level. SSVEP amplitudes were depressed in both glaucoma groups, more so in the moderate to severe glaucoma group. The differences between controls and the moderate-severe glaucoma groups were more statistically reliable for decrements than for increments. Mean responses to decremental sawtooth stimuli were larger than those to increments in controls and in the mild glaucoma but not in the moderate to severe glaucoma group at the first harmonic. OFF/decrement responses at the first harmonic were faster in controls, but not in patients.

Conclusions

The observed pattern of preferential loss of decremental responses in human glaucoma is consistent with prior reports of selective damage to OFF retinal ganglion cells in murine models and in data from human ERG and retinal imaging. These data motivate pursuit of SSVEP as a biomarker for glaucoma progression.

Applications of the isolated-check visual evoked potential in primary open angle glaucoma with or without high myopia

AIM

To explore the diagnostic performance of isolated-check visual evoked potential (icVEP) for primary open angle glaucoma (POAG) in both highly myopic and non-highly myopic populations and compare it with those of optical coherence tomography (OCT) and Heidelberg retinal tomography (HRT) parameters.

METHODS

A total of 126 participants were recruited, including 31 highly myopic participants with POAG (HM-POAG), 36 non-highly myopic participants with POAG (NHM-POAG), 25 highly myopic participants without POAG (HM) and 34 controls without high myopia (Normal). All the participants underwent a complete ophthalmic examination. The signal-to-noise ratio (SNR) was used to assess the icVEP. Both qualitative and quantitative diagnostic performances of OCT, HRT and the icVEP were analyzed and compared.

RESULTS

Based on the criterion of SNR≤1, the diagnostic performance of the icVEP in highly myopic subjects [area under the receiver operating characteristic curve (AUC)=0.862] was better than that in non-highly myopic subjects (AUC=0.789), and the SNR had fairly good specificity. In distinguishing the HM-POAG and HM groups, the AUC of the SNR was not different from those of the OCT and HRT parameters (P>0.05) in either the qualitative or quantitative comparison. In the qualitative analysis, the icVEP showed good consistency with damage to the central 10° of the visual field (kappa=0.695-0.747, P<0.001).

CONCLUSION

The icVEP has the potential to discriminate individuals with and without POAG, especially in populations with high myopia.

Isolated-check visual evoked potential: a more sensitive tool to detect traumatic optic neuropathy after orbital fracture

PURPOSE

To establish a more sensitive diagnostic tool for traumatic optic neuropathy (TON), we explored the diagnostic efficacy of isolated-check visual evoked potential (ic-VEP) for TON in orbital fracture and compared ic-VEP with pattern-reversal visual evoked potential (P-VEP) testing.

METHODS

This was a prospective single-center study. A total of 137 eyes from 131 patients diagnosed between December 2016 and October 2019 with orbital fractures were included in the study. Injury history, best-corrected visual acuity (BCVA), visual field, computed tomography (CT), P-VEP, and ic-VEP data were collected. Parameters of ic-VEP (signal-to-noise ratio [SNR]) and P-VEP (peak latency and amplitude of P100) were compared and diagnostic accuracy was analyzed.

RESULTS

TON was associated with worse BCVA than non-TON (median 0.52 versus 0.10 logMAR, P < 0.001). SNRs were negatively associated with the P100 peak latency while positively associated with the P100 amplitude. The sensitivity of ic-VEP for TON (79.6%) was higher than that of P-VEP (61.2%, P = 0.049), although this difference was not statistically significant after Bonferroni correction. Using ic-VEP and P-VEP together could increase sensitivity (87.8%). Maximum areas under curve were obtained using the SNR criteria of 1.3, 1.47, and 1.54 at 8%, 16%, and 32% depth of modulation, respectively.

CONCLUSION

ic-VEP was more sensitive than P-VEP in diagnosing TON, and a combination of the two examination tests was recommended. The use of ic-VEP as the new diagnostic standard technique for TON should be considered.

Dynamics of Contrast Decrement and Increment Responses in Human Visual Cortex

Purpose

The goal of the present experiments was to determine whether electrophysiologic response properties of the ON and OFF visual pathways observed in animal experimental models can be observed in humans.

Methods

Steady-state visual evoked potentials (SSVEPs) were recorded in response to equivalent magnitude contrast increments and decrements presented within a probe-on-pedestal Westheimer sensitization paradigm. The probes were modulated with sawtooth temporal waveforms at a temporal frequency of 3 or 2.73 Hz. SSVEP response waveforms and response spectra for incremental and decremental stimuli were analyzed as a function of stimulus size and visual field location in 67 healthy adult participants.

Results

SSVEPs recorded at the scalp differ between contrast decrements and increments of equal Weber contrast: SSVEP responses were larger in amplitude and shorter in latency for contrast decrements than for contrast increments. Both increment and decrement responses were larger for displays that were scaled for cortical magnification.

Conclusions

In a fashion that parallels results from the early visual system of cats and monkeys, two key properties of ON versus OFF pathways found in single-unit recordings are recapitulated at the population level of activity that can be observed with scalp electrodes, allowing differential assessment of ON and OFF pathway activity in human.

Translational Relevance

As data from preclinical models of visual pathway dysfunction point to differential damage to subtypes of retinal ganglion cells, this approach may be useful in future work on disease detection and treatment monitoring.

Discovery and clinical translation of novel glaucoma biomarkers

Glaucoma and other optic neuropathies are characterized by progressive dysfunction and loss of retinal ganglion cells and their axons. Given the high prevalence of glaucoma-related blindness and the availability of treatment options, improving the diagnosis and precise monitoring of progression in these conditions is paramount. Here we review recent progress in the development of novel biomarkers for glaucoma in the context of disease pathophysiology and we propose future steps for the field, including integration of exploratory biomarker outcomes into prospective therapeutic trials. We anticipate that, when validated, some of the novel glaucoma biomarkers discussed here will prove useful for clinical diagnosis and prediction of progression, as well as monitoring of clinical responses to standard and investigational therapies.

Applications of Isolated-Check Visual Evoked Potential in Early Stage of Open-Angle Glaucoma Patients

Background:

Standard automated perimetry does not sufficiently detect early open-angle glaucoma (OAG) in the clinic. New visual function tests for early glaucoma damage are therefore needed. The present study evaluated whether an isolated-check visual evoked potential (icVEP) could be used to detect visual function abnormalities in early-stage OAG and to explore potential related factors.

Methods:

This was a cross-sectional study. Thirty-seven OAG patients with early-stage visual field loss (mean deviation ≥ −6.00 dB) detected by the Humphrey Field Analyzer (30-2 SITA program) and 26 controls were included in this study. Optical coherence tomography (OCT) was used to detect retinal nerve fiber layer (RNFL) defects. The icVEP preferentially evaluates the magnocellular-ON pathway. VEPs were recorded and signal-to-noise ratios (SNRs) were derived based on multivariate analysis. Eyes that yielded an SNR ≤1 were considered abnormal. Receiver operating characteristic (ROC) curve analysis was used to estimate the accuracy of group classification. Correlations between SNRs and related factors were analyzed.

Results:

Based on an SNR criterion of 1, the icVEP had a sensitivity of 62.2% and a specificity of 92.3% for diagnosing early-stage OAG with 74.6% classification accuracy. The ROC curve analysis, however, suggested that an SNR criterion of 0.93 would produce the highest classification accuracy (77.3%). Both RNFL thinning in the temporal superior quadrant on OCT and number of abnormal test points in the central 11° visual field (pattern deviation, P < 0.5%) significantly correlated with the SNR (P < 0.05).

Conclusions:

The icVEP detected visual function abnormalities in approximately 3/5 of eyes with early-stage OAG with greater than 90% specificity. SNR correlated with both a decrease in RNFL thickness and severity of central visual field loss.