This document discusses VEP (visually evoked potential) testing for evaluating the visual pathway from the eye to the brain. It describes how VEP works by measuring the electrical signal from the retina to the visual cortex in response to visual stimuli. Key points covered include the components of the VEP waveforms, how different stimuli test different visual pathways, and examples of how VEP can help evaluate conditions like glaucoma, optic neuritis, and amblyopia. The document also notes how advances in technology have made VEP more widely available in clinical practice.

1. VEP For The 21st Century
Jody Abrams, MD
Sarasota Retina Institute

2. Disclosures
 I do neuro-ophthalmology so no financial
disclosures
 I do refuse to wear a bowtie
 We do own one of the VEP machines

3. VEP For The 21st Century
The SRI Update course baby

4. VEP For The 21st Century
 VEP: visually evoked potential, visually evoked
response, and visually evoked cortical potential
 Electrical impulse from the eye to the brain
 Part of an EEG

5. VEP For The 21st Century

6. VEP For The 21st Century
 Functional integrity of entire visual pathway
 Anterior Segment to Visual Cortex

7. VEP For The 21st Century
 First noticed during strobe lights with early EEGs in
the 30s
 Computers were able to extract the visual
potentials with signal averaging
 Similar to anti-radar jamming programs in the 50s
 Saves defined time period of activity and averages
out the randomness

9. VEP For The 21st Century
 Electrical signal for VEP is 1-20 microvolts
 Computer’s data acquisition is synchronized to
the timing of the visual stimulus
 Apply signal averaging to repeated stimuli and
the wave form is captured

10. VEP For The 21st Century
 Pattern reversal stimulation is preferred testing
stimuli
 Black and white checker board alternates
 Light output remains the same
 VEP response is from detection of edges between
the white and black areas

12. VEP For The 21st Century
 First negative peak is N75
 First positive peak is P100
 Second negative peak is
N135

13. VEP For The 21st Century
 Amplitude is amount of
energy reaching the
cortex
 Difference between N75
and P100
 Normal is around 6
microvolts for 32x32 board

14. VEP For The 21st Century
 Amplitude gives how much information is making
it to the occipital lobe
 Increase often can indicate better discrimination
 Refraction can be a big issue with this

15. VEP For The 21st Century
 Latency is the time it takes to get the information
back to the occipital lobe
 P100 is peak of the information getting to the
visual cortex
 Average is 100 ms (97-117)

16. VEP For The 21st Century
 Latncy is increased by impedance in conduction
 Less variation then amplitude

17. VEP For The 21st Century
 Most common pattern is checkered board or
bars
 Best response in normal patients at 32x32
pattern size
 Adjust for level of vision

18. VEP For The 21st Century
 Contrast is adjusted for cell bias
 High contrast for parvocellular
 Low contrast for magnocellular

19. VEP For The 21st Century
 Parvocellular cells most
abundant
 Sensitive to color
 Help with discriminating fine
detail

20. VEP For The 21st Century
 Magnocellular cells
 Coarse vision
 Motion
 More sensitive with low contrast
 Thought to be damaged in
early glaucoma

21. VEP For The 21st Century
 Flash VEP good for extreme vision loss or if not
able to focus on screen
 Look at N2 (90 ms) and P2 peaks (120ms)

22. VEP For The 21st Century
 Machines used to be
complicated
 Mostly reserved to
universities

24. VEP For The 21st Century
 Computer advancements
 More compact system
 Easier tech work
 Interpretation easier

25. VEP For The 21st Century
 Now in ophthalmology offices, optometry
offices, and neurology clinics
 Use has exploded
 Need to at least know what it means

26. VEP For The 21st Century
 VEP is a tool
 Does not give the
diagnosis
 A “semi” objective way
to track change

27. VEP For The 21st Century
 VEP ignores the appearance
 It looks at how the system runs

28. VEP For The 21st Century
 Amblyopia
 Glaucoma
 Traumatic Brain Injury
 Optic Neuritis/MS
 Other causes of optic nerve dysfunction
 Functional visual loss
 Dense cataracts

30. VEP For The 21st Century
 55 y/o BF
 Family hx of glaucoma
 IOP 21/19
 Corneal thickness 555/542

31. VEP For The 21st Century
 Angles open
 C/D 0.7 ou

32. VEP For The 21st Century
 HVF normal OU
 SD-RNFL 92 and 88
 Would you treat?

34. VEP For The 21st Century
 34 y/o obese WF
 Headaches
 Sent with dx of PTC
 On Diamox 500 bid
 Denies visual complaints

35. VEP For The 21st Century
 VA 20/25 ou
 Pupils no APD, no light/near disassociation, brisk


37. VEP For The 21st Century
 Is it time to rush to OR for a nerve sheath
fenestration or VP shunt?
 Can the Diamox be increased and watch
closely?

39. VEP For The 21st Century
 32 WF
 1 s/p delivery with eclampsia
 Now has LP vision ou
 Pupils brisk, no APD, no LND
 CF unreliable

40. VEP For The 21st Century
 -9 myopia ou
 Tilted Optic nerves
 OCTs show thinning but difficult scan secondary
to optic nerve anatomy

41. VEP For The 21st Century
 Is this a real problem?
 Refuses MRI
 OB/GYN feels is faking it to get attention

43. Posterior reversible encephalopathy syndrome

44. VEP For The 21st Century
 89 yo WM
 Sent over for abnormal VF and VEP
 Pt has not noticed visual change
 Original fields appeared to have Left
homonymous hemianopia

46.  This lead to MRI
which was read as
normal
 A VEP was done

47. VEP For The 21st Century
 Our Exam
 20/25 ou
 Pupils no APD, no L/N, brisk
 Fundus showed Dry ARMD

48. RNFL
OD 103
OS 107

49.  VEP does not give all the answers
 Make sure getting good data
 If it does not make sense with all the other
information repeat the test

50.  CPT code 95930