Electrodiagnostics Handout March 20183/9/18 4 ¨ Low contrast testing demonstrates degradation of magnocellular pathways ¡ An early indication of glaucoma ¨ High contrast testing

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Nate Lighthizer, O.D., F.A.A.OAssociate Professor, NSUOCO

Assistant Dean for Clinical Care ServicesDirector of CE

Chief of Specialty Care Clinics

¨ What is electrodiagnostics testing?¨ Visual Pathway – Basic Understanding

¨ VEP¨ pERG¨ ffERG¨ mfERG

¨ Clinical Cases

¨ AKA Visually Evoked Response (VER)¡ Flash vs. Pattern

¨ Measures the entire visual pathway¡ From cornea to occipital lobe

¨ 3 electrodes¡ Ground¡ Reference¡ Measuring -> occipital lobe

ú 1” above inion

Reference Ground Active

VEP Electrodes

LATENCY(ms) AMPLITUDE(µv)

• Amplitude usually translates to the amount of axons conducting along the visual pathway

• Latency usually translates to the myelin status of the visual pathway

VEP

¨ Many optic nerve diseases are asymptomatic because central vision is not affected until late in the disease1

¨ Diagnosis and management of optic nerve disorders are often based on structural or subjective visual field tests2

1 Glaucoma. American Optometric Association. www.aoa.org2 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

VEP is an objective, functional test that can help discriminate between healthy and glaucomatous eyes2

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Structure FunctionFundusPhotograph

(Subjective)VisualField(Subjective)

IOP18mmHg

VisualAssessment

IOP18mmHgIOP26mmHgTreatmentinitiation

Structure FunctionOpticalCoherenceTomography

(Objective)ERG&VEP(Objective)

IOP26mmHgTreatmentinitiation

IOP18mmHg

DynamicVisualFunctionAssessment

IOP18mmHg






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“Increased pattern VEP latency was significantly correlated with both the severity and location of visual field defects and the degree of cupping and pallor of the optic disc.” The authors of this paper are world

recognized electrophysiology specialist form New England Medical Center and University of Chicago

“The finding that is of clinical importance is the presence of abnormally long VEP latencies in some patients with ocular hypertension. The abnormal prolongation of VEP latency in these eyes may reflect subclinical optic nerve lesions that have not been uncovered with other techniques.”

¨ Repeatability of short-duration transient visual evoked potentials in normal subjects. Tello C, De Moraes CG, Prata TS, Derr P, Patel J, Siegfried J, Liebmann JM, Ritch R. Doc Ophthalmol. 2010 Jun;120(3):219-28. Epub 2010 Jan 29.

¨ Short Duration Transient Visual Evoked Potentials in Glaucomatous Eyes. Prata TS, Lima VC, De Moraes CG, Trubnik V, Derr P, Liebmann JM, Ritch R, Tello C. J Glaucoma. 2011 May 10. [Epub ahead of print]

¨ Short-duration transient visual evoked potential for objective measurement of refractive errors. Anand A, De Moraes CG, Teng CC, Liebmann JM, Ritch R, Tello C. Doc Ophthalmol. 2011 Dec;123(3):141-7. Epub 2011 Sep 20.

dead Suffering Alive

Glaucoma

VEP

OCTHRTGDX

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. 2009 Sep;247(9):1223-33. Epub 2009 Mar 17.

Alive

Glaucoma

VEP

OCTHRTGDX

Alivedead







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¨ Low contrast testing demonstrates degradation of magnocellular pathways¡ An early indication of glaucoma

¨ High contrast testing demonstrates degradation of parvocellular pathways ¡ An early indicator of central vision loss and issues

caused by problems before signal reaches optic nerve

**patient should be tested with best corrected vision**

ASSESSMENT OF NEURO-VISUAL FUNCTION ASSESSMENT OF NEURO-VISUAL FUNCTION


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¨ VEP is an objective, functional test that can help discriminate between healthy and diseased eyes

¨ Indications:¡ Glaucoma¡ MS/Optic neuritis¡ Optic neuropathies¡ Unexplained vision loss¡ Transient vision loss¡ Visual field defects¡ Amblyopia/Strabismus¡ Traumatic brain injury

¨ ERG’s are electrical signals that are a measure of the electrophysiological activity at the retina¡ ***Mid-retinal layers, ganglion cell layer, and nerve fiber

layer***

¨ Objectively measures retinal function**

¨ ERG’s can help improve sensitivity and specificity in diagnosing optic neuropathies and maculopathies like glaucoma and macular degeneration when used in conjunction with other tests

¨ Can also help the clinician differentiate between retinal and optic nerve disorders when used in conjunction with Visual Evoked Potential (VEP).

1. Concentric Stimulus Fields¡ Drug toxicity¡ Diabetic macular edema¡ AMD

2. Contrast Sensitivity¡ Glaucoma¡ Diabetic retinopathy

1. Concentric Stimulus Fields¡ Stimulus delivered at 15 flips/second¡ BCVAú Pt should be properly refracted for 24”

¡ 24” testing distance¡ 100% contrast

¡ Right eye (OD) then Left Eye (OS)ú 25 seconds at 24 degreesú 25 seconds at 16 degrees

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2. Contrast Sensitivity¡ Stimulus delivered at 15 flips/second¡ BCVAú Pt should be properly refracted for 24”

¡ 24” testing distance¡ 85% and 15%

¡ Right eye (OD) then Left Eye (OS)ú 25 seconds at High Contrast (Hc)ú 25 seconds at Low Contrast (Lc)

“In patients who are glaucoma suspects, pERG signal anticipates an equivalent loss of OCT signal by several years (as many as 8 years).Invest Ophthalmol Vis Sci. 2013;54:2346-2352) DOI:10.1167/iovs.12-11026

VEP ERG OCT VF

% of cell loss

0% 100%

• ERG shown to detect glaucoma while cells are alive, up to 8 years before OCT. (IOVS, 2013; Mar;54(3): 2346-52)• VEP may be able to detect glaucoma slightly earlier than ERG as the disease is shown to affect LGN before retina

(PNAS: 2010 Mar)• SAP requires approx 30% (6% to 57% range) cell death to register peripheral vision loss (Ophthalmology: 2013

Apr;120(4):736-44)• OCT detects glaucoma approximately 2 to 3 years before VF with about 15% RNFL loss (Est)

DiseaseCCTIOP

Healthy Cells

You Are Missing a Big Valuable Piece of the Puzzle!

Sick but Viable

dead Suffering Alive

Glaucoma

VEP

OCTHRTGDX


Alive

Glaucoma

VEP

OCTHRTGDX

Alivedead


“In patients who are glaucoma suspects, pERG signal anticipates an equivalent loss of OCT signal by several years (as many as 8 years).Invest Ophthalmol Vis Sci. 2013;54:2346-2352) DOI:10.1167/iovs.12-11026

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¨ Glaucoma¨ Optic Neuropathies ¨ Maculopathies

¡ AMD¡ Diabetic retinopathy¡ Diabetic macular edema¡ Macular toxicity

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Operator: Salazar,Andres Eye Centers of Florida, PA #2 - 4771

Comments: - Grating Size: 64 Signature:

Diagnosis is doctor's responsibility. PERG recorded using skin electrodes. (16,12,23,15)Copyright © 2015 Diopsys, Inc. All Rights Reserved. Software Version: 2.18.5118-VX

First Name: Kathryn DOB: 11/16/1979Last Name: Coiro Age: 35Patient ID: Gender: FemaleExam Date: 2015-05-11 OD:+1.50 BCVA: 20/30Exam Time:03:32:10 PM OS:+1.50 BCVA: 20/15

OD Signal Quality:

OS 62dBµV 60Hz noise

Time (ms)0 20 40 60 80 100 120 140 160 180 200

24°

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Time (ms)0 20 40 60 80 100 120 140 160 180 200

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Parameter OD 24° OD 16° OS 24° OS 16°

Magnitude (uV) 3.90 2.45 3.73 2.28

MagnitudeD 3.66 2.31 3.61 2.09

MagD/Mag Ratio 0.94 0.94 0.97 0.92

SNR (dB) 14.3 10.9 14.1 9.6

Artifacts 1 0 5 2

MagnitudeD

Operator: Salazar,Andres Eye Centers of Florida, PA #2 - 4771



First Name: Kathryn DOB: 11/16/1979Last Name: Coiro Age: 35Patient ID: Gender: FemaleExam Date: 2015-05-11 OD:+1.50 BCVA: 20/30Exam Time:03:32:10 PM OS:+1.50 BCVA: 20/15

OD Signal Quality:


Time (ms)0 20 40 60 80 100 120 140 160 180 200

24°

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Time (ms)0 20 40 60 80 100 120 140 160 180 200

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Time (ms)0 20 40 60 80 100 120 140 160 180 200

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Magnitude (uV) 3.90 2.45 3.73 2.28

MagnitudeD 3.66 2.31 3.61 2.09

MagD/Mag Ratio 0.94 0.94 0.97 0.92

SNR (dB) 14.3 10.9 14.1 9.6

Artifacts 1 0 5 2

Scott Wehrly, MDOperator: Rivas,Nicole Lake Eye Associates - 9448



Last Name: ALLAIRE DOB: 1/9/1943First Name: SANDA Age: 72Patient ID: 460 Gender: FemaleExam Date: 2015-07-14 OD:+1.00 +0.75 x75 BCVA: 20/20Exam Time:01:16:32 PM OS:+1.00 +0.50 x95 BCVA: 20/20

OD Signal Quality:


Time (ms)0 20 40 60 80 100 120 140 160 180 200

24°

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Time (ms)0 20 40 60 80 100 120 140 160 180 200

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Magnitude (uV) 1.01 1.25 1.24 1.17

MagnitudeD 0.75 0.46 0.72 0.54

MagD/Mag Ratio 0.74 0.37 0.58 0.46

SNR (dB) 0.3 2.4 2.3 1.3

Artifacts 1 0 0 0

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ValueasaPrognosticIndicationofProgressionofOHTtoGlaucoma

VisualFieldandFDT:25-50%sensitivity

OCT:approximately70%

PERG:77%

NormalPERGResponse

Magnitude,MagnitudeD andMagD/MagRatioarecolorized.

GreenindicateswithinnormallimitsYellowindicatesvaluesareborderlineRedindicatesoutsidenormallimits

3QuickStepsToReportInterpretationSignalQuality– Lookforagreensignal

SinusoidalPeaks– Lookfor3humps

PERGReport– DataTable

Magnitude(uV)isdefinedasthestrengthofthepatient’sresponseatareversalrateof15reversalspersecond.

Largermagnitudesaretypicallygeneratedfromnormaleyes.Smallermagnitudestypicallyindicatepathology.

Asthecontrastleveldropsorthestimulussizedecreases,themagnitudewilltypicallydecrease.


MagnitudeD averagesthesignalwithinthe25secondtesttimeandtakesintoaccountthemagnitudestrengthandthephasevariabilitythroughoutthetest.

Inahealthypatient,thephaseresponsetendstobeconsistentthroughoutthetest.Inthiscase,MagD iscloseinvaluetoMag.

Inapatientwithdisease,thephaseresponsetendstobeinconsistentthroughoutthetest-MagD willbesignificantlyreducedincomparisonwithMag.


MagD/MagRatioisthemostrepeatablemeasurementtest-over-test.Theclosertheratioisto1.0,thelowerthephasevariabilitythroughoutthetest,andthehealthierthepatient’sresponse.Variabilityinphasemayindicatepathology.

MagD/Magratiocanusedtomonitorpatientsovertime.

DataTable

SNR- SignaltoNoiseRatioshowshowstrongthesignalisat15Hzcomparedtonoiseat15Hz.LargernumbersindicatestrongerPERGsignalscomparedtothenoise.

SNRvalueslike5,15,>20showstrongPERGresponse.Numberslessthan2aretypicalofaweakresponse.

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DataTable

Artifactsarecausedbyblinkingorpatientmovement.Theyaredetectedandcounted.Ahighnumberofartifactswilleffecttheamountofdatathatcanbeanalyzed.

Thegoalistohavealownumberofartifacts.Wewantthepatienttobecomfortableandblinkwhennecessary,butnotexcessively.Thegoalislessthan10.IftestsresultsshowArtifactsgreaterthan10,thetestshouldberepeated.

AbnormalPERG

Missing3humps

Yellowindicatesvaluescomparedtonormalareborderline

Redindicatesvaluesareoutsidenormallimits

StimulusMini-ganzfeld Photoreceptors&Bipolar

FlickerElectroretinogram(FlickerERG)

Retinalsignalrecordedatthe

lowerlidinresponsetoflash

stimuliofhighfrequency

¨ Tests the outer retina ¡ Photoreceptors (rod & cones)¡ Bipolar cells

¨ Test of overall retinal functioning¡ May not pick up small retinal issues

¨ Flash flicker stimulus

BCVA2-3°

OCT 12°

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mfERG21°Flicker ERG

Full Field

¨ Tests the outer retina ¡ Photoreceptors (rod & cones)¡ Bipolar cells

¨ Test of overall retinal functioning¡ May not pick up small retinal issues

¨ Flash flicker stimulus

¨ ffERG indications:¡ DM & diabetic retinopathy

ú Monitoring progressionú Monitoring improvement with treatment

¡ Retinal dystrophies/diseaseú Rod/cone problems ú RP

¡ Pt symptoms:ú Color vision issuesú VF defectsú Decreased visionú Unexplained decreased vision

¡ Testing retinal function with significant media opacities¡ Indicator for prognosis following cataract surgery

ú Is the retina functioning well or not?

ERGforEarlyDetection ERGforEvaluatingRetinalDysfunction

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FlickerERGforTreatmentEvaluation

FlickerERGReproducibilityICCinHealthyeyes

Protocol Parameter ICC

FlickerERG Magnitude 0.93

Phase 0.98

WillsEyeHospital,ARVO2016

RetinalEvaluationinEyeswithCRVO

ERG vs FA : Predictive value of Vascularization

FA:52%ERG:94%

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Flicker ERG is a good predictor of ischemia

Flicker ERG can be used to evaluate DR

Flicker ERG can be used to monitor patients and evaluate referals

Healthy Dysfunction

FlickerERGReport

Magnitude isthecone/bipolarsignalstrength

Phaseisthetimingofthecone/bipolarresponse

MagnitudeandPhaseVariancerepresenttheconsistencyofthestrengthandspeedofthesignal

respectively

FlickerERGReport

Magnitude areaisthecone/bipolarcombinedsignalstrengthofthe6

luminancelevels

Phaseareaisthecone/bipolarcombinedsignaltimingofthe6

luminancelevels

MacularFunctionEvaluationinEyesWithoutCataracts

Ganzfeld

1. Ratanapakorn T, Patarakittam T, Sinawat S, Sanguansak T, Bhoomibunchoo C, Kaewpanna S, Yospaiboon Y.Effectofcataractonelectroretinographic response.JMedAssocThai. 2010;93:1196-9.

2. Pérez-SalvadorGarcíaE, PérezSalvadorJL.Variabilityofelectrophysiologicalreadingsinmaturecataracts.ArchSocEsp Oftalmol. 2002;77:543-51.

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MacularFunctionEvaluationinEyesWithCataracts

Ganzfeld

Cataract

1. Ratanapakorn T, Patarakittam T, Sinawat S, Sanguansak T, Bhoomibunchoo C, Kaewpanna S, Yospaiboon Y.Effectofcataractonelectroretinographic response.JMedAssocThai. 2010;93:1196-9.

2. Pérez-SalvadorGarcíaE, PérezSalvadorJL.Variabilityofelectrophysiologicalreadingsinmaturecataracts.ArchSocEsp Oftalmol. 2002;77:543-51.

MacularFunctionEvaluationinEyesWithCataracts

Cataract

ISCEV*RecommendusingERGfortheevaluationofretinalfunctioninpatientswithmediaopacities.

*(InternationalSocietyofClinicalElectrophysiologyofVision)

iscev.org/standards/proceduresguide.html

VEP FFERG1. Glaucoma & glaucoma

suspects2. Unexplained vision

loss3. Transient vision loss4. Unexplained VF

defects 5. Unreliable VF6. Optic neuropathies7. Optic neuritis/MS8. Amblyopia9. TBI

1. DM & retinopathy2. RP & its variants3. Cone dystrophies

& Rod monochromat

4. Symptoms:¡ “Night blindness”¡ Restricted

peripheral fields¡ Color vision

deficits¡ Unexplained

decreased vision5. To get an idea of

retinal functioning in a pt with media opacity

PERG1. Glaucoma &

glaucoma suspects2. Unexplained VF

defects 3. Unreliable VF4. Optic neuropathies5. Maculopathies

1. AMD2. Diabetic macular

edema3. High risk med use

(Plaquenil)4. Generalized DR

Nate Lighthizer, O.D., F.A.A.OAssistant Professor, NSUOCO

Assistant Dean for Clinical Care ServicesDirector of CE

Chief of Specialty Care ClinicsChief of Electrodiagnostics Clinic

Documents

Electrodiagnostics Handout March 20183/9/18 4 ¨ Low contrast testing demonstrates degradation of magnocellular pathways ¡ An early indication of glaucoma ¨ High contrast testing