VISUAL EVOKED POTENTIAL PATTERN ELECTRORETINOGRAM ASSESSMENT OF NEURO VISUAL FUNCTION. Lee Shettle, D.O. Lee Shettle Eye & Hearing

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1 VISUAL EVOKED POTENTIAL PATTERN ELECTRORETINOGRAM ASSESSMENT OF NEURO VISUAL FUNCTION Lee Shettle, D.O. Lee Shettle Eye & Hearing

2 Overview of VEP / PERG Why should I Use this Test? How does it work? Clinical Indications of VEP & PERG Interpretation Case presentations Billing & Coding

3 Electrocardiogram

4 ELECTROPHYSIOLOGY Electrocardiogram Electromyography Auditory Evoked Potential Electroencephalogram

5 Previous Ocular Electrophysiological Testing Limitations Test time was approximately 45 minutes Required highly trained operators Limited to large research institutions

6 Ophthalmic Diagnostic Tests Psychophysical VF GDx HRT OCT

7 Psychophysics of vision Visual Acuity Test

8 Psychophysics of vision Color Vision Test

9 Psychophysics of vision Visual Field Test

10 Psychophysics of vision Contrast Sensitivity Test

11 Current Conditions Test time is approximately 1 minute Does not require highly trained operators Provides valuable Objective Functional data Currently installed in about 700 offices

12 Where are we Testing? Low contrast testing demonstrates degradation of Magnocellular pathways An early indication of glaucoma, peripheral disease High contrast testing demonstrates degradation of parvocellular pathways An early indicator of central vision loss and issues mostly caused by problems before signal reaches optic nerve, ie central macular disease **patient should be tested with best corrected vision**

13 Why Use VEP? Many optic nerve diseases are asymptomatic because central vision is not affected until late in the disease 1 Diagnosis and management of optic nerve disorders are often based on structural or subjective visual field tests 2 VEP is an objective, functional test that can help discriminate between healthy and glaucomatous eyes 2 1 Glaucoma. American Optometric Association. 2 Prata, Tiago MD, G. De Moraes MD, J. Liebmann MD, R. Ritch, C. Tello MD. (2009). Diagnostic Ability of Fast Transient Visual Evoked Potential for Glaucoma Assessment [Poster & Abstract] American Academy of Ophthalmology. 128

14 Before Treatment OCT HRT GDX VEP dead Suffering Alive Effect of epigallocatechin-gallate on inner retinal function in ocular hypertension and glaucoma: a short-term study by pattern electroretinogram. Graefes Arch Clin Exp Ophthalmol Sep;247(9): Epub 2009 Mar 17. Glaucoma

15 After Treatment OCT HRT GDX VEP dead Alive Alive Effect of epigallocatechin-gallate on inner retinal function in ocular hypertension and glaucoma: a short-term study by pattern electroretinogram. Graefes Arch Clin Exp Ophthalmol Sep;247(9): Epub 2009 Mar 17. Glaucoma

16 Science Made Simple Visual Evoked Potential (VEP) Visual patient observes a visual stimulus Evoked generates electrical energy at the retina Potential measure the electrical activity in the visual cortex Objectively measure the function of the entire vision system; no verbal response or button pushing required

17 NEURO PHYSIOLOGY Phototransduction Conversion of light into electricity

18 ANATOMY Photoreceptor Bipolar Ganglion Ganglion cell axon Relay neuron Relay neurons axon Visual cortex neuron

19 NEURO PHYSIOLOGY Light Photoreceptor Phototransduction Electricity Bipolar Electricity Ganglion cell axon Electricity Relay neuron Electricity VEP Visual cortex neuron

20 VEP Main Indications Glaucoma Multiple Sclerosis Ischemic Optic Neuropathy Traumatic Brain Injury Amblyopia Other Neuropathies

21 ISCEV International Society for Clinical Electrophysiology of Vision

22 VEP Stimulus Diffuse Pattern Reversal Pattern onset Transient Steady State

23 VEP TEST VEP should be done with refractive correction for 39 Uncorrected Multifocal Monofocal

24 Diopsys NOVA-LX

25 VEP Testing Protocols NOVA-LX Advanced Protocol Testing distance of 39 Alternating 32 x 32 HC & LC Checkerboard pattern NOVA-TR User Defined Protocol Testing distance of x 16, 8 x 8, 4 x 4 HC & LC Check size Alternating HC & LC Checkerboard Pattern

26 VEP Electrode Placement Reference Ground Active

27 ASSESSMENT OF NEURO-VISUAL FUNCTION VEP Electric signal registered at the occipital region in response to a visual stimulus. Electrical activity of V1 occipital cortex

28 VEP Components P100 Amplitude usually translates to the number of axons conducting along the visual pathway N75 N135 Latency usually translates to the myelin status of the visual pathway

29 VEP LX Interpretation 32 x 32 checkerboard Standard Protocol Amplitude - >6 microvolts P 100 High Contrast Latency using 85% High contrast stimulus - 95 to 117 ms. P 100 Low Contrast Latency using 15% Low contrast stimulus ms P100 Reliability Index >70% minimum

30 Diopsys VEP Report

31 Diopsys VEP Report

32 Diopsys VEP Report

33 Diopsys VEP Report

34 Diopsys VEP Report

35 Diopsys VEP Report

36 Diopsys VEP Report

37 Diopsys VEP Report

38 VEP - Abnormal

39 VEP - Abnormal

40 VEP abnormal - Asymmetry