Identifying preperimetric functional loss in glaucoma: a blue-on-yellow multifocal visual evoked potentials study

Multifocal Visual Evoked Potential (mfVEP) and Pattern-Reversal Visual Evoked Potential Changes in Patients with Visual Pathway Disorders: A Case Series

The purpose of this study was to evaluate multifocal visual evoked potential (mfVEP) and pattern-reversal visual evoked potential (PVEP) changes in patients with pathology at various levels of the visual pathway determined by other methods. Six patients with different visual pathway disorders, including vascular ischaemic events and compressive optic neuropathy, were reviewed. All patients were tested with both mfVEP and full-field and half-field PVEPs. Results were assessed in relation to other diagnostic tests such as magnetic resonance imaging, Humphrey visual field test, and optical coherence topography. The cases in this study demonstrate a potential higher sensitivity of mfVEP compared with conventional PVEPs in detecting lesions affecting the peripheral field, horizontal hemifields, and lesions of the post-chiasmal pathway. The limitation of the PVEP in this setting is probably due to phase cancellation and overrepresentation of the macular region. mfVEP provides a more accurate assessment of visual defects when compared with conventional PVEP. The independent assessment of different areas of the visual field improves the detection and localization of lesions and provides an objective topographical map that can be used in clinical practice as an adjunct to other diagnostic tests and to assess disease progression.

Multifocal visual evoked potentials for early glaucoma detection

BACKGROUND AND OBJECTIVE

To compare multifocal visual evoked potentials (mfVEP) with other detection methods in early open-angle glaucoma.

PATIENTS AND METHODS

Ten patients with suspected glaucoma and 5 with early open-angle glaucoma underwent mfVEP, standard automated perimetry (SAP), short-wave automated perimetry, frequency-doubling technology perimetry, and nerve fiber layer optical coherence tomography. Nineteen healthy control subjects underwent mfVEP and SAP for comparison. Comparisons between groups involving continuous variables were made using independent t tests; for categorical variables, Fisher's exact test was used.

RESULTS

Monocular mfVEP cluster defects were associated with an increased SAP pattern standard deviation (P = .0195). Visual fields that showed interocular mfVEP cluster defects were more likely to also show superior quadrant nerve fiber layer thinning by OCT (P = .0152).

CONCLUSION

Multifocal visual evoked potential cluster defects are associated with a functional and an anatomic measure that both relate to glaucomatous optic neuropathy.

Application of multifocal visual evoked potentials in the assessment of visual dysfunction in macular diseases

PURPOSE

To evaluate the use of AccuMap multifocal visual evoked potentials (mfVEP) in visual dysfunction caused by macular diseases.

METHODS

Forty-eight eyes with known macular diseases underwent AccuMap mfVEP and microperimetry 1 (MP1) assessments. Evaluation of mfVEP abnormality was based on an amplitude deviation probability plot and the AccuMap Severity Index (ASI). Correlation analyses of the mean mfVEP amplitude corresponding to a radius of 2°, 5°, and 10° of the central visual field, minimum angle of resolution best-corrected visual acuity (BCVA), and MP1 mean sensitivity of the corresponding areas were performed.

RESULTS

Among the 48 affected eyes, AccuMap mfVEP detected an abnormality of the central visual field in 45 eyes, with a sensitivity of 93.8%. The mean mfVEP amplitudes within a radius of 2°, 5°, and 10° of the central visual field were found to be positively correlated with BCVA (P<0.01 for all groups). The mean amplitudes also positively correlated with the MP1 mean sensitivity value of the corresponding visual field (P<0.01 for all groups). In the group with stable fixation or predominantly central fixation, the mean mfVEP amplitudes did not correlate with the BCVA or the MP1 mean sensitivity value. Regardless of the fixation status, the ASI was found to correlate with both the BCVA and the total MP1 mean defect value.

CONCLUSION

Objective perimetry using AccuMap mfVEP might be applied in the assessment of macular function, with the ASI offering a potentially useful indicator for evaluating macular dysfunction.

Simultaneous recording of multifocal VEP responses to short-wavelength and achromatic stimuli

A paradigm is introduced that allows for simultaneous recording of the pattern-onset multifocal visual evoked potentials (mfVEP) to both short-wavelength (SW) and achromatic (A) stimuli. There were 5 sets of stimulus conditions, each of which is defined by two semi-concurrently presented stimuli, A64/SW (a 64% contrast achromatic stimulus and a short-wavelength stimulus), A64/A8 (64% achromatic/8% achromatic), A0/A8 (0% (gray) achromatic/8% achromatic), A64/A0 and A0/SW. When paired with A64 as part of A64/SW, the SW stimulus yielded mfVEP responses (SWmfVEP) with diminished amplitude in the fovea, consistent with the known sensitivity of the S-cone system. In addition, when A8, which is approximately equal to the L and M cone contribution of the SW stimulus, was recorded alone, the response to A8 was small, but significantly larger than noise. However, when A8 was paired with A64, the response to A8 was reduced to close to noise level, suggesting that the LM cone contribution of the SWmfVEP can be suppressed by A64. When A64 was recorded alone, the response to A64 was about 32% larger than the mfVEP for A64 when paired with the SW. Likewise, the presence of A64 stimulus also reduces the response of SWmfVEP by 35%. Finally, an intense narrow-band yellow background prolonged the latency of SW response for the A0/SW stimulus but not the latency of SW response for the A64/SW stimulus. These results indicate that it is possible to simultaneously record an SWmfVEP with little LM cone contribution along with an achromatic mfVEP.