Download - Multifocal VEP: insights into the optic neuropathies Save Sight Institute University of Sydney
Multifocal VEP: insights into Multifocal VEP: insights into the optic neuropathiesthe optic neuropathies
Save Sight Institute Save Sight Institute
University of SydneyUniversity of Sydney
MFVEP- unique diagnostic MFVEP- unique diagnostic testtest
Distinct from conventional VEPDistinct from conventional VEP Topographic informationTopographic information Finer and more complete samplingFiner and more complete sampling
More than a perimetric testMore than a perimetric test AmplitudeAmplitude LatencyLatency
Insights into pathophysiology of optic Insights into pathophysiology of optic pathway diseasespathway diseases
Compare FFVEP & MFVEPCompare FFVEP & MFVEP
50 degrees
Multifocal VEP
“Full-field” VEP
FFVEP & MFVEPFFVEP & MFVEP
Preservation of peripheral mfVEP
Absent
Normal eye Optic Neuritis
FF VEP
MF VEP
FFVEP & MFVEPFFVEP & MFVEPNormal Traumatic optic neuropathy
Preserved ff VEP
mfVEP – significant losses, central inferior signal preserved
What is Multifocal VEP and how What is Multifocal VEP and how it works? it works?
Multifocal VEP stimulation and Multifocal VEP stimulation and recordingrecording
Striate cortex Visual field
L Calcarine fissure R
Recording channels
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+ -
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+
Extraction of mfVEP by cross-Extraction of mfVEP by cross-correlationcorrelation
Clinical application of multifocal VEP Clinical application of multifocal VEP in glaucomain glaucoma
Why pursue objective Why pursue objective testing ?testing ?
Limitations of subjective Limitations of subjective teststests High level of co-operation High level of co-operation
requiredrequired Variable performanceVariable performance Learning curveLearning curve Patient complaints – stressfulPatient complaints – stressful Late detection of Late detection of
glaucomatous damage glaucomatous damage
Using achromatic Using achromatic stimulation various types stimulation various types
of scotoma can be of scotoma can be identifiedidentified
sensitivity of the technique:sensitivity of the technique:
in in early glaucoma 90-95% early glaucoma 90-95% in moderate to advance in moderate to advance
glaucoma-100%glaucoma-100%
(at specificity of 95%)(at specificity of 95%)
Example of glacoma patient with unreliable Example of glacoma patient with unreliable subjective visual field and normal optic disc-subjective visual field and normal optic disc-
mfVEP normalmfVEP normal
Sparse pattern-onset Sparse pattern-onset
stimulationstimulation Bright yellow backgroundBright yellow background Blue checks Blue checks
To improve mfVEP sensitivity in early To improve mfVEP sensitivity in early glaucoma Blue-on-Yellow Stimulation was glaucoma Blue-on-Yellow Stimulation was
introducedintroduced
It demonstrated:It demonstrated:100% sensitivity in early perimetric glaucoma 100% sensitivity in early perimetric glaucoma 95% specificity95% specificityLarger defects compared to black-and-white Larger defects compared to black-and-white mfVEP for the same eyes, especially in very mfVEP for the same eyes, especially in very early defectsearly defects
Blue-on-Yellow mfVEP was then applied Blue-on-Yellow mfVEP was then applied to pre-perimetric glaucoma to pre-perimetric glaucoma
14 out of 30 patients with pre-perimetric 14 out of 30 patients with pre-perimetric glaucoma had mfVEP defectsglaucoma had mfVEP defects
In all 14 cases, location of mfVEP defects In all 14 cases, location of mfVEP defects
corresponded topographicallycorresponded topographically with the with the worst affected rimworst affected rim
Example 1 of Example 1 of pre-perimetricpre-perimetric glaucoma glaucoma
Example 2 of Example 2 of pre-perimetricpre-perimetric glaucoma glaucoma
New stimulation technique New stimulation technique for simultaneous for simultaneous
BINOCULAR recording BINOCULAR recording using Virtual Reality using Virtual Reality
GogglesGoggles
MfVEP can be successfully used to MfVEP can be successfully used to detect visual field defect detect visual field defect
MfVEP can identifies defects in nearly MfVEP can identifies defects in nearly 50% patients with pre-perimetric 50% patients with pre-perimetric glaucoma which corresponded to glaucoma which corresponded to structural changes structural changes
ConclusionConclusion
R
Glaucoma subject
-Right eye scotoma
-Left eye normal VF
L
Utility of multifocal VEP in Utility of multifocal VEP in
optic neuritis.optic neuritis.
1. Multi-focal VEP amplitude as a marker of extent and evolution of inflammation in acute stage of ON
10 days-amplitude extinguished across whole field except temporal paracentral area
20 days- amplitude extinguished in the rest of the field, but begins to recover at some peripheral locations
1 month-significant recovery of amplitude in areas of visual field initially affected
2 month-amplitude still reduced in temporal paracentral area
3 month-almost complete amplitude recovery, small relative depression remains in temporal paracentral area
2. Multi-focal VEP amplitude as a marker of axonal
recovery/degeneration in post-acute stage of ON
Patient JL-”not-MS”
Monitoring axonal recovery-1Monitoring axonal recovery-1
1 month after ONASI=196
3 monthASI=140
6 monthASI=78
12 monthASI=39
1 month
3 month
6 month
12 month
MC-”MS”
Monitoring axonal degenerationMonitoring axonal degeneration
Example of gradual amplitude loss
3. Using multi-focal VEP to determine 3. Using multi-focal VEP to determine degree and topography of demyelinationdegree and topography of demyelination
Latency analysis of individual Latency analysis of individual segmentssegments
Non-affected eye
Affected eye
Detecting demyelination
Non-affected eye
Affected eye
complete amplitude recovery but significant complete amplitude recovery but significant delaydelay
1 m post-ON
Latency delay
4. Using multi-focal VEP to 4. Using multi-focal VEP to monitor remyelinationmonitor remyelination
VEP traces Amplitude Ampl asymmetry Latency Latency asymmetry
Example of good latency recoveryExample of good latency recovery
ConclusionConclusionThe mfVEP may be used to track The mfVEP may be used to track recovery of function in optic neuritisrecovery of function in optic neuritis
The rate and extent of functional recovery of The rate and extent of functional recovery of both amplitude and latency may have both amplitude and latency may have significance in terms of underlying significance in terms of underlying pathological processes, and ultimate pathological processes, and ultimate prognosis for conversion to MSprognosis for conversion to MS
It may be possible to use the mfVEP as a It may be possible to use the mfVEP as a monitor for remyelination in patients monitor for remyelination in patients undergoing treatment for early diseaseundergoing treatment for early disease