Accuracy of isolated-check visual evoked potential technique for diagnosing primary open-angle glaucoma

Early impairment of magnocellular visual pathways mediated by isolated-check visual evoked potentials in primary open-angle glaucoma: a cross-sectional study

OBJECTIVE

To explore different performances in the magnocellular (MC) and parvocellular (PC) visual pathways in patients with primary open-angle glaucoma (POAG) and to objectively assess impairment in early stage of POAG.

METHODS AND ANALYSIS

This is a cross-sectional study. MC and PC visual pathways were assessed using isolated-check visual evoked potential (ic-VEP). Visual acuity, intraocular pressure, fundus examination, optical coherence tomography and visual field were measured. Signal-to-noise ratios (SNRs), mediated by ic-VEP were recorded. The Spearman's correlation analysis was used to estimate the relationships between visual functions and structures. Receiver-operating-characteristic (ROC) curves were used to estimate the accuracy in detection of early POAG.

RESULTS

60 participants (30 early POAG eyes and 30 age-matched control subjects) were recruited. MC visual pathway showed a non-linear response function, while PC visual pathway was a linear response function as contrast increased. Early POAG eyes exhibited significantly weaker initial contrast gains and lower maximum responses in the MC visual pathway (p=0.001, p=0.004, respectively). The SNRs at 8% and 32% depths of modulation (DOM) were significantly correlated with temporal-side retinal nerve fibre layer (RNFL) thickness in early POAG in MC-biased stimulation (p=0.017, p=0.020, respectively). The areas under ROC of 16% DOM were 0.780 (sensitivity 80.0%, specificity 63.3%) with the cut-off SNR of 2.07.

CONCLUSIONS

The MC visual pathway was damaged in the early stage of POAG. The SNRs at 8% and 32% DOM of MC-biased stimulation were significantly correlated with temporal-side RNFL thickness in early POAG, which helped in understanding the mechanisms of visual impairment in the early stage of POAG.

Utility of isolated-check visual evoked potential technique in dysthyroid optic neuropathy

PURPOSE

To analyze the utility of isolated-check visual evoked potential (icVEP) for discriminating between eyes with dysthyroid optic neuropathy (DON) and eyes with thyroid-associated ophthalmopathy (TAO) but not DON.

METHODS

Forty-three eyes with TAO but not DON (as non-DON), fifty-three eyes with DON, and sixty healthy eyes (as controls) were included. Comprehensive ophthalmic examinations, including best-corrected visual acuity, refraction, color vision test, intraocular pressure measurement, slit-lamp biomicroscopy, ophthalmoscopy, RAPD, exophthalmometry measurements, pVEP test, icVEP test, standard automated perimetry, and clinical activity score classification of TAO, as well as demographic information, were collected and analyzed.

RESULTS

In the DON group, the signal-to-noise ratio (SNR) value of icVEPs decreased significantly compared with that of the non-DON group as well as control (p < 0.05). The SNR values under 8%, 16% and 32% depth of modulation (DOM) were significantly negatively correlated with BCVA (p < 0.05, r =  - 0.9 ~  - 0.6), papilledema (Y/N) (p < 0.05, r =  - 0.8 ~ 0.4) and DON (Y/N) (p < 0.001, r =  - 0.7 ~  - 0.5). The 8% DOM of icVEP had the largest area under the receiver operating characteristic curve (AUC) (0.842) for discriminating DON from non-DONs. Meanwhile, decision curve analysis (DCA) showed that patients clinically benefit most from 8% DOM of icVEP. Furthermore, the 8% DOM of icVEP combing with papilledema (Y/N) and BCVA (Model 1) has significantly larger AUC than the 8% DOM of icVEP (p = 0.0364), and has better clinical benefit in DCA analysis.

CONCLUSIONS

The SNR of 8% DOM from icVEP may represent a significant ancillary diagnostic method for DON detection. Furthermore, icVEP combined with papilledema (Y/N) and BCVA should be considered as a diagnostic model in future clinical practice.

Diagnostic Capability of Isolated-Check Visual Evoked Potential for Early to Moderate Primary Open-Angle Glaucoma

This study aimed to evaluate the diagnostic capability of isolated-check visual evoked potential (icVEP) for primary open-angle glaucoma (POAG) via comparison with visual field (VF) tests and pattern visual evoked potential (PVEP). This cross-sectional study enrolled 68 subjects, including 33 POAG patients and 35 controls. All subjects underwent a complete ophthalmic examination, including icVEP, PVEP, and VF tests. The diagnostic performance, the area under the receiver operating characteristic curve (AUC), the integrated discrimination index (IDI), and the net reclassification index (NRI) were calculated. The clinical benefits of the three tests were compared via decision curve analysis (DCA) of the signal-to-noise ratio (SNR) from icVEP, the P100 latency and amplitude of 1° and 0.25° checks from the PVEP, pattern standard deviation (PSD), and mean deviation (MD) from the VF test. The SNR, MD and PSD, PVEP P100 latency of 0.25° checks, and P100 amplitude (both 1° and 0.25° checks) showed significant differences between the POAG and control groups (* p < 0.05), except for the P100 latency of 1° checks. Regarding diagnostic ability, the three tests, AUC, IDI, and NRI, showed no significant difference (p > 0.05). The DCA showed that the clinical benefits of icVEP (SNR) were comparable to those of VF (MD and PSD) and better than those of PVEP (P100 latency and amplitude). In addition, no significant difference was found in the consistency analysis of the qualitative comparison between the icVEP, VF, and PVEP (McNemar p > 0.05). In this study, icVEP showed a diagnostic ability for early to moderate POAG patients comparable to VF and PVEP. IcVEP might be applied as a supplementary psychophysical examination method in addition to VF examinations for special POAG populations who have difficulty cooperating with the VF examination.

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.

Central visual function and inner retinal structure in primary open-angle glaucoma

To investigate associations between central visual function and inner retinal structure in primary open-angle glaucoma (POAG). This study enrolled 78 POAG patients and 58 healthy controls. POAG was classified into early glaucoma and moderate to advanced glaucoma. The following tests were performed on all participants: isolated-check visual evoked potential (icVEP) testing, 24-2 standard automated perimetry (SAP), and Cirrus optical coherence tomography (OCT) examinations. Signal-to-noise ratio (SNR) measures obtained from icVEP responses to isolated checks presented at four depths of modulation (DOMs; 8%, 14%, 22%, and 32%) were explored. Mean macular sensitivity (mMS) was assessed by calculating the mean sensitivities of central 12 SAP points. Ganglion cell layer+ inner plexiform layer thickness (GCL+IPLT) and peripapillary retinal nerve fiber layer thickness (pRNFLT) were measured by OCT scanning. For each group of subjects, linear relationships among the following measures were analyzed: SNR, mMS, GCL+IPLT, and pRNFLT. SNR, mMS, GCL+IPLT, and pRNFLT were all more significantly decreased in glaucoma than in controls (P<0.001). A significant positive association was found between SNR at 14% DOM and GCL+IPLT at the inferior sector in early glaucoma (r=0.465, P=0.004). In moderate to advanced glaucoma, significant correlations were found between SNR at 32% DOM and mean GCL+IPLT (r=0.364, P=0.023), superior GCL+IPLT (r=0.358, P=0.025), and mean pRNFLT (r=0.396, P=0.025). In addition, in moderate to advanced glaucoma, there were significant correlations between mMS and all relevant measures of retinal thickness (r=0.330-0.663, P< 0.010). In early glaucoma, significant correlations were found between mean mMS and minimum GCL+IPLT (r=0.373, P=0.023), and between inferior mMS and superior GCL+IPLT (r=0.470, P=0.003). Linear models provided a good explanation for the relationship between SNR and inner retinal thickness (IRT), whereas nonlinear models better explained the relationship between mMS and IRT. In early glaucoma, both SNR and mMS were related moderately and significantly to IRT, whereas in moderate to advanced glaucoma, mMS was more strongly correlated with IRT than SNR.

Application of electrophysiological tests in the evaluation of early thyroid-associated ophthalmopathy

PURPOSE

To compare the electrophysiology between mild thyroid-associated ophthalmopathy (TAO) patients and normal population.

METHODS

The present research was a retrospective observational study and enrolled consecutive patients diagnosed with mild TAO according to European Group on Graves's Orbitopathy with corrected to normal vision. Full-field electroretinography, pattern visual evoked potential (PVEP) and isolated-check visual evoked potential (icVEP) were performed for TAO patients and age-matched normal subjects.

RESULTS

Thirty-two eyes with mild TAO and forty-six eyes from normal subjects were included. Statistically significant increase in the amplitude of dark-adapted 0.01, 3 and 10 ERG and total oscillatory potentials and light-adapted 3 and 30 Hz flicker ERG were observed in TAO patients compared with the normal subjects, but not the latency. No significant difference was observed in the P100 amplitude or latency in 1° and 15' PVEP between TAO patients and normal subjects. The signal-to-noise ratio (SNR) was not significantly different in TAO patients at the contrast of 1%, 2%, 8%, 16% or 32% icVEP, and the SNR in contrast 4% icVEP was significantly smaller in TAO patients compared to normal subjects.

CONCLUSION

Mild TAO patients can have electrophysiological changes that might indicate neural changes in the early disease phase.

Comparing isolated-check visual evoked potential, pattern visual evoked potential, and standard automated perimetry in dysthyroid optic neuropathy eyes

Objective

To determine the diagnostic ability of isolated-check visual evoked potential (icVEP), pattern visual evoked potential (pVEP), and standard automated perimetry (SAP) between dysthyroid optic neuropathy (DON) and thyroid-associated ophthalmopathy (TAO) without DON (non-DON).

Methods

This is a case-control study, 49 bilateral patients (26 DON and 23 non-DON) were included. icVEP, pVEP, and SAP were conducted in all the subjects, icVEP parameters compared were signal-to-noise ratios (SNRs) under 8, 16, and 32% depth of modulation (DOM). pVEP parameters compared were amplitude and latency. SAP parameters were mean deviation (MD) and pattern standard deviation (PSD). The area under the receiver operating characteristic (ROC) curve (AUC), net reclassification index (NRI), integrated discrimination index (IDI), and decision curve analysis (DCA) were applied for analysis.

Results

In icVEP, values of SNR in DON were significantly smaller than non-DON (p < 0.05). In pVEP, P100 latent time in DON was significantly larger than non-DON (p = 0.0026). In SAP, value of PSD in DON was larger than non-DON (p = 0.0006), and value of MD in DON was smaller (p = 0.0007). AUC, NRI, and IDI among the three tests were not significantly different. DCA showed that SNR of icVEP under 8% DOM was the farthest from the two extreme curves.

Conclusions

icVEP, pVEP, and SAP have equal diagnostic capabilities to discern between DON and non-DON. In addition, icVEP may represent a significant ancillary diagnostic approach to DON detection, with more clinical benefit.

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.

Electrophysiology in Glaucoma

OBJECTIVES

Electrophysiological testing of the visual system has been continuously used in studies involving the evaluation of retinal ganglion cells and the diagnosis of glaucoma. This study aims to review the results of recent studies regarding the clinical applicability of electrophysiological tests to glaucoma.

METHODS

A systematic review of the literature was carried out by 2 independent reviewers using the PubMed and EMBASE electronic databases, searching for articles published in English from January 1, 2014 to July 1, 2019 using a combination of the following keywords: ("glaucoma" OR "ocular hypertension") AND ("electrophysiolog" OR "electroretinogra" OR "ERG" OR "mfERG" OR "Pattern-reversal electroretinography" OR "PERG" OR "mfPERG" OR "photopic negative response" OR "pattern electroretinogram" OR "visual evoked potential" OR "multifocal electroretinography" OR "multifocal electroretinogram" OR "electro-oculography" OR "multifocal VEP" OR "mf-ERG"). A total of 38 studies were selected and the data of 30 of them were tabulated in this review.

RESULTS

Among the 30 studies selected, the photopic negative response and the reversal pattern electroretinogram were found to be the major methods used to record the electroretinographic responses generated by the retinal ganglion cell. Their multifocal versions and the multifocal visual evoked potential were also proposed during this period. In general, the results underscored a consistent but general correlation between the amplitude and latency measures and routine tests for glaucoma, such as perimetry and optical coherence tomography.

DISCUSSION

In agreement with previous reviews, clinical electrophysiological testing of the visual system reasonably matched with both the structural and functional analyses for glaucoma. No definitive indications of these tests have been established either at early detection or during follow-up of the disease, and easier protocols and better topographical correspondence with current glaucoma tests are warranted for their routine use.

Objective Assessment of the Effect of Optical Treatment on Magnocellular and Parvocellular-biased Visual Response in Anisometropic Amblyopia

Purpose

Optical treatment can improve visual function in anisometropic amblyopia, but there is no electrophysiological evidence, and the underlying change in visual pathway remains unknown. Our aims were to characterize the functional loss in magnocellular and parvocellular visual pathways in anisometropic amblyopia at baseline and to investigate the effect of optical treatment on the 2 visual pathways.

Methods

Using isolated-check visual-evoked potential, we measured the magnocellular- and parvocellular-biased contrast response functions in 15 normal controls (20.13 ± 3.93 years; mean ± standard deviation), 16 patients with anisometropic amblyopia (18.00 ± 6.04 years) who were fully refractive corrected before and 29 (19.41 ± 7.41 years) who had never been corrected. Twelve previously uncorrected amblyopes received optical treatment for more than 2 months and finished the follow-up measurement.

Results

Both the magnocellular- and parvocellular-biased contrast response functions in the amblyopic eye exhibited significantly reduced response and weaker contrast gains. We also found that the uncorrected amblyopes showed a more severe response reduction in magnocellular-biased, but not parvocellular-biased condition when compared with those corrected, with a weaker initial contrast gain and lower maximal response. After optical treatment, 12 uncorrected amblyopes demonstrated improved visual acuity of the amblyopic eye and a significant response gain to magnocellular-biased but not parvocellular-biased stimuli.

Conclusions

We demonstrated deficits to both magnocellular- and parvocellular-biased stimuli in subjects with anisometropic amblyopia. Optical treatment could produce neurophysiological changes in visual pathways even in older children and adults, which may be mediated through the magnocellular pathway.

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.

Visual Evoked Potentials and Glaucoma

Visual evoked potentials (VEP) can be used to assess the function of the visual system objectively. Research on VEP testing as a method of glaucoma evaluation has been performed for many years. Pattern VEP has shown good specificity and sensitivity in the detection of glaucoma in some studies, but other studies have not shown similar efficacy. Multifocal VEP can produce a topographical measure of glaucomatous damage and has been shown to be able to detect a similar number of defects in patients with glaucoma or ocular hypertension as compared with the visual field test. Despite promising data on these VEP test modalities in the assessment of glaucoma, multiple aspects of test administration make their routine use impractical in a clinical setting. New VEP testing modalities, such as short-duration transient VEP and isolated-check VEP, allow the test to be performed more quickly and easily. Further research on these more recent technologies may allow us to use VEP effectively in the diagnosis and management of glaucoma.