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

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

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

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

5. FFVEP & MFVEP NormalTraumatic 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 fissure R 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 Limitations of subjective tests High level of co-operation required High level of co-operation required Variable performance Variable performance Learning curve Learning curve Patient complaints – stressful Patient complaints – stressful Late detection of glaucomatous damage Late detection of glaucomatous damage

12. Using achromatic stimulation various types of scotoma can be identified sensitivity 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. Sparse pattern-onset stimulation Sparse pattern-onset stimulation Bright yellow background Bright yellow background Blue checks Blue checks To improve mfVEP sensitivity in early glaucoma Blue-on-Yellow Stimulation was introduced 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 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 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. MfVEP can be successfully used to detect visual field defect 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 MfVEP can identifies defects in nearly 50% patients with pre-perimetric glaucoma which corresponded to structural changes Conclusion

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

21. Utility of multifocal VEP in optic neuritis.

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

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

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

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

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

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