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Multifocal VEP: insights into the optic neuropathies

Multifocal VEP: insights into the optic neuropathies. Save Sight Institute University of Sydney. MFVEP- unique diagnostic test. Distinct from conventional VEP Topographic information Finer and more complete sampling More than a perimetric test Amplitude Latency

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Multifocal VEP: insights into the optic neuropathies

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  1. Multifocal VEP: insights into the optic neuropathies Save Sight Institute University of Sydney

  2. MFVEP- unique diagnostic test • Distinct from conventional VEP • Topographic information • Finer and more complete sampling • More than a perimetric test • Amplitude • Latency • Insights into pathophysiology of optic pathway diseases

  3. 50 degrees Compare FFVEP & MFVEP Multifocal VEP “Full-field” VEP

  4. FFVEP & MFVEP Normal eye Optic Neuritis Absent FF VEP MF VEP Preservation of peripheral mfVEP

  5. FFVEP & MFVEP Normal Traumatic optic neuropathy Preserved ff VEP mfVEP – significant losses, central inferior signal preserved

  6. What is Multifocal VEP and how it works?

  7. Multifocal VEP stimulation and recording

  8. Striate cortex Visual field _ + L Calcarine fissureR + - _ + Recording channels

  9. Extraction of mfVEP by cross-correlation

  10. Clinical application of multifocal VEP in glaucoma

  11. Why pursue objective testing ? • Limitations of subjective tests • High level of co-operation required • Variable performance • Learning curve • Patient complaints – stressful • Late detection of glaucomatous damage

  12. Using achromatic stimulation various types of scotoma can be identifiedsensitivity of the technique: in early glaucoma 90-95% in moderate to advance glaucoma-100%(at specificity of 95%)

  13. Example of glacoma patient with unreliable subjective visual field and normal optic disc-mfVEP normal

  14. To improve mfVEP sensitivity in early glaucoma Blue-on-Yellow Stimulation was introduced • Sparse pattern-onset stimulation • Bright yellow background • Blue checks • It demonstrated: • 100% sensitivity in early perimetric glaucoma • 95% specificity • Larger defects compared to black-and-white mfVEP for the same eyes, especially in very early defects

  15. Blue-on-Yellow mfVEP was then applied to pre-perimetric glaucoma • 14 out of 30 patients with pre-perimetric glaucoma had mfVEP defects • In all 14 cases, location of mfVEP defects corresponded topographically with the worst affected rim

  16. Example 1 of pre-perimetric glaucoma

  17. Example 2 of pre-perimetric glaucoma

  18. New stimulation technique for simultaneous BINOCULAR recording using Virtual Reality Goggles

  19. Conclusion • MfVEP can be successfully used to detect visual field defect • MfVEP can identifies defects in nearly 50% patients with pre-perimetric glaucoma which corresponded to structural changes

  20. Glaucoma subject • Right eye scotoma • Left eye normal VF R L

  21. Utility of multifocal VEP in optic neuritis.

  22. Multi-focal VEP amplitude as a • marker of extent and evolution of • inflammation in acute stage of ON

  23. 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

  24. 2. Multi-focal VEP amplitude as a marker of axonal recovery/degeneration in post-acute stage of ON

  25. Monitoring axonal recovery-1 1 month after ON ASI=196 3 month ASI=140 6 month ASI=78 12 month ASI=39 Patient JL-”not-MS”

  26. Monitoring axonal degeneration 1 month 3 month 6 month Example of gradual amplitude loss 12 month MC-”MS”

  27. 3. Using multi-focal VEP to determine degree and topography of demyelination

  28. Latency analysis of individual segments Non-affected eye Affected eye

  29. Detecting demyelination complete amplitude recovery but significant delay Non-affected eye Latency delay Affected eye 1 m post-ON

  30. 4. Using multi-focal VEP to monitor remyelination

  31. Example of good latency recovery VEP traces Amplitude Ampl asymmetry Latency Latency asymmetry

  32. Conclusion The mfVEP may be used to track recovery of function in optic neuritis The rate and extent of functional recovery of both amplitude and latency may have significance in terms of underlying pathological processes, and ultimate prognosis for conversion to MS It may be possible to use the mfVEP as a monitor for remyelination in patients undergoing treatment for early disease

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