erg and vep lecture sept 20, 2015

ERG and VEP for NEURO-VISUAL FUNCTION ASSESSMENT

J. Alberto Martinez, M.D.

CURRENT REALITY• BY THE TIME WE DIAGNOSE GLAUCOMA, THE

PATIENT HAS HAD IT FOR 5 YEARS! (or more)

“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

Per NIH and Bascom-Palmer

ASSESSMENT OF NEURO-VISUAL FUNCTION

Neuro-visual Pathway Function Review1. Anatomy at glance2. Neuro-physiology at glance

Electrophysiology3. Visual Evoked Potential (VEP) concepts4. VEP hardware and software5. VEP obtaining and interpreting6. Other electrophysiological tests\Clinical VEP7. Glaucoma8. MS9. Amblyopia10.Cataract11.Other

Continued

INDEX

VEP and Function Tests1. VA, CS, CV2. VF

VEP and Structure Tests3. HRT, GDxOCTINDEX

PERG4. Basics5. Clinical usage of

PERG6. Retino-cortical

time.Q & A


Eye

Optic Nerve

Optic ChiasmOptic TractLateral Geniculate Nucleus

Optic Radiation

Visual Cortex

ANATOMY


ANATOMY

PhotoreceptorBipolarGanglion

Ganglion cell axon

Relay neuron

Relay neurons axon

Visual cortex neuron


NEURO-PHYSIOLOGY

Phototransduction

Conversion of light into electricity


VEP

Photoreceptor

Ganglion cell axon

Relay neuron

Visual cortex neuron

NEURO-PHYSIOLOGY

Bipolar

Light

Phototransduction

Electricity

Electricity

Electricity

Electricity


ELECTROPHYSIOLOGY

• Electrocardiogram

• Electromyography

• Auditory Evoked

Potential

• Electroencephalogram


Electric signal registered at the

occipital region in response to a

visual stimulus.


VEP

Electrical activity of V1 occipital

cortex

Electric signal registered at the lower

lid in response to a visual stimulus.


PERG

Electrical activity of retinal ganglion

cells


Previous Limitations

• Test time was approximately 45

minutes

• Required highly trained operators

• Limited to large research institutions


• Test time is approximately 1

minute

• Does not require highly

trained operators

• Currently installed in about

700 offices worldwide

Current Conditions

VEP Stimulus

• Diffuse

• Pattern

Reversal

Pattern-onset

Transient

Steady State


• Diffuse Pattern

Reversal

Pattern-onset

Contrast

Color



Why would VEP show a functional change on patients with 20/20?

20/20

20/200

20/10020/50

20/30

20/70

20/100

20/10020/25


N75

N135

P100

VEP Components


N75

N135

P100

VEP Components

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

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

Diopsys® VEP Report


Main Indications

• Glaucoma

• Multiple Sclerosis

• Ischemic Optic Neuropathy

• Traumatic Brain Injury

• Amblyopia

• Other Neuropathies


VEP

VEP and other Ophthalmic Diagnostic Tests

• Psychophysics• VF• GDx• HRT• OCT


Psychophysics of vision

Visual Acuity Test



Contrast Sensitivity Test



Color Vision Test



Visual Field Test


ERG mERG pERG mVEP EOG

Electroretinogram Multifocal ElectroretinogramPattern ElectroretinogramMultifocal Visual Evoked PotentialElectrooculogram

Electrophysiological tests



N35

N95

P50

PERG GENERALConcept

Pattern Electroretinography is the electrical signal registered at the eye because of a pattern stimulation of the retina.


Stimulus(Monitor)

Recording(Sensors)

Eye stimulation by a checkerboard pattern elicits a ganglion cell

response known as PERG.

PERG is an accurate and objective indicator of

ganglion cell and macular function.

(ISCEV)

PERG can detect retinal dysfunction (OHT) before

structural tests.(Parisi et al.)

pERG


PERG GENERAL

ERG

PERG

Q

24”24.1°

Stimulation Monitor


PERG TEST

WRONG


ReproducibilityFactors able to affect the PERG results

• Refraction errors

• IOP

• Diabetes M

• Patient Attention

• Technique

PERG TEST


PERG TEST

MonofocalMultifocal

PERG should be done with refractive correction for 24”

Uncorrected

Diopsys® pERG Electrodes

Comfort Convenience Quality



Active for OSReference for OD

Active for ODReference for OS

Ground

Sensors Position

PERG TEST


PERG TEST

Active Skin Sensor Placement

Step 1.Sensor positioning.

Eyelashes

Eyelid Skin


PERG TEST

Active Skin Sensor Placement

Step 2.Sensor positioning.

Eyelashes

Eyelid Skin


Electrodes Picture Cost ($) Position Amplitude Repeatability Visual Axis Disturbance

Overall Discomfort

Usage

DTL 13 Conjunctiva (invasive)

***** Sensitive to eye movements (noise)

** *** Disposable

HK Loop 35 Conjunctiva (invasive)


** *** Reusable

Gold Foil 10 Conjunctiva (invasive)


** *** Disposable

Gold Cup 13 Skin *** Good ** ** Reusable

Diopsys 11 Skin *** Good * * Disposable

ELECTRODES COMPARISON


PERG TEST

Q

Protocols

1. VEP TR

2. VEP LX

3. PERG Manual

4. PERG Auto


Concentric Fields 24° and 16°PERG TEST


Contrast Sensitivity (higher and lower contrast)PERG TEST


PERG

Main Indications

• Glaucoma

• Maculopathies


PERG CLINIC

Vision problem of unknown cause

VEP

PERG

Differentiating between optic nerve and retinal disorders

Manual

TR


PERG Report


PERG Report

Magnitude DMagnitude D


PERG Report

Grating Size: 64


PERG CLINIC

Vision problem of unknown cause

VEP

PERG

Differentiating between optic nerve and retinal disorders


PERG CLINIC

Normal

Ischemic

Compressive

Toxic

inflammatory

Glaucoma

Nutritional

Hereditary

Q


Banitt MR, Ventura LM, Feuer WJ, Savatovsky E, Luna G, Shif O, Bosse B, Porciatti V. Progressive loss of retinal

ganglion cell function precedes structural loss by several years in glaucoma suspects. Invest Ophthalmol Vis

Sci. 2013;54:2346-52.

IOP Genetic

Oxidative StressNeurotoxicityHypoxia

/Users/jalbertomartinez/Desktop/Suffering ganglion cells.png


Structure FunctionFundus Photograph

(Subjective)Visual Field(Subjective)


Structure FunctionOptical Coherence Tomography

(Objective)Pattern ERG(Objective)

Healthy

Asymptomatic Symptomatic

VF

Glaucoma

Ellish NJ, Higginbotham EJ. Evaluating a visual field screening test for glaucoma: how the choice of the gold standard affects the validity of the test. Ophthalmic Epidemiol. 2001 Dec;8(5):297-307.


Healthy

Asymptomatic Symptomatic

VF

Glaucoma

OCT

Documented structural damageNon documented structural damage

Schuman JS, Hee MR, Arya AV, Pedut-Kloizman T, Puliafito CA, Fujimoto JG, Swanson EA. Optical coherence tomography: a new tool for glaucoma diagnosis. Curr Opin Ophthalmol. 1995 Apr;6(2):89-95.


Healthy

VF

Glaucoma

OCT

Documented structural damageNon documented structural damage

PERG/VEP

Documented functional damageNon documented functional damage

Parisi V, Miglior S, Manni G, Centofanti M, Bucci MG. Clinical ability of pattern-electroretinograms and visual evoked potentials in detecting visual dysfunction in ocular hypertension and glaucoma. Ophthalmology. 2006 Feb;113(2):216-28.


OHT


PERG CLINICMaculopathies


pERG CLINICGlaucoma Detection


pERG CLINICGanglion Cell Function Recovery


pERG CLINICMacular Function Recovery


PERGPERG provides information about the functionality of the ganglion cells in the retina.

PERG provides information about reversibility of the ganglion cells functionality.

PERG provides the earliest information about ganglion cells dysfunctional.

Thanks

Q & A


erg and vep lecture sept 20, 2015

Health & Medicine