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Dr Frank FAMOSE

DVM, CES Ophtalmologie

Ekaterinburg May 2010

ELECTRORETINOGRAPHY

What is electroretinography ?

►Fonctionnal activity Low voltage electrical activity

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History

►1849 : Dipolar activity of eye (Dubois-Raymond)

►1865 : Electrical activity of retina (Holmgren)

►1924 : First recordings of human ERG (L�wenstein)

►1933 : ERG components (Granit)

►1967 : ERG applications in Vet ophthalmology (Rubin)

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Retinal electrophysiology

►Receptor level : hyperpolarisation

►Post-receptor level Bipolar cells : depolarisation or hyperpolarisation Horizontal cells : hyperpolarisation Amacrine cells : transitory hyperpolarisation Ganglionar cells : depolarisation or hyperpolarisation

►Pre-receptor level : depolarisation after hyperpolarisation

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General morphology of ERG

General morphology of ERG

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General morphology of ERG

a-wave : receptor levelb-wave : post-receptor levelc-wave : pre-receptor level

c c

Other waves :Oscillatory potentials (OP)Early Receptor Potential (ERP)

The components of ERG

►From Granit’s work : 3 components Pigmentary epithelium Ganglionar cells Photoreceptors

►Intra-retinal potentials a-wave : Photoreceptors b-wave : bipolar cells depolarisation c-wave : pigmentary epithelium

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Electroretinography material

►Light stimulation Intensity Spectral composition Spatial repartition Repetition frequency

►Filters Neutral Coloured

Electroretinography material

►Electrodes Active electrode Reference electrode Ground electrode

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►Collecting and recording data Amplification Filtration Computer

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Electroretinography material

Variations in components of ERG : photoreceptors

►Rods Low light intensity Low frequency Rhodopsine Saturation process

►Cones High light intensity High frequency (>30Hz) 2 spectral sensitivities No saturation

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Variations in components of ERG : intensity of light stimulation

►Standardisation

►Effects of increased intensity

►Spectral composition

►Time frequency

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Variations in components of ERG : environmental light conditions

►Scotopic conditions (darkness) Rods in dim flash Cones in strong flash

stimulation

►Photopic conditions (daylight conditions) Saturation of rods Specific stimulation

of cones

Dim flash of blue lightDim flash of blue lightin darkness conditionsin darkness conditions

Stimulation of rods onlyStimulation of rods only

Strong flash of achromatic lightStrong flash of achromatic lightin darkness conditionsin darkness conditions

Saturation of rodsSaturation of rodsSpecific evaluation of conesSpecific evaluation of cones

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Variations in components of ERG : anesthesia

►Necessity of

anesthesia

►Effects of inhalation

anesthaetics

►Effects of hypoxia

Variations in components of ERG : the patient

►Pupillary size :

mydriasis

►Age : attenuation

►Ocular opacities :

various effects

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ERG protocols

►Goals of the ERG Selective stimulation

►Animal preparation Mydriatics General anesthesia

►Electrodes fixation Active electrode Reference electrode Ground electrode

ERG protocols : ISCEV

►Only white stimulation►Darkness adaptation

(20 min)►Dim stimulation in

scotopic conditions►Photopic stimulation in

photopic conditions►Photopic stimulation in

30 hz frequency

Rods stimulation

Rods and cones stimulation

Cones stimulation

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ERG protocols : coloured stimulations

►Darkness adaptation (20 min)

►Dim blue stimulation in scotopic conditions

►Photopic red stimulation in photopic conditions

►Photopic white stimulation in 30 hz frequency

Rods stimulation

Cones stimulation

Cones stimulation

ERG protocols : « mix » protocol

►Room light adaptation (2 hours)

►Photopic white stimulation

►Darkness adaptation (20 min)

►Scotopic blue stimulation in darkness

►Photopic stimulation in 30 hz frequency Cones stimulation

Rods stimulation

Cones stimulation

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ERG : other techniques

►Multifocal ERG►Pattern ERG

For Human and laboratory use

ERG analysis

►Waves amplitude►Time of culmination

No reference value !!

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One month later…

ERG analysis

Clinical indications of ERG

►Preoperative

evaluation of retina

(cataract surgery)

►Amaurosis

►Clinical evaluation of

retina in pathologic

conditions

►Early diagnosis of

retinal conditions

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Conclusion

►Fonctionnal evaluation of global retinal

activity

►Numerous factors of variation

►Needs pratice and standardisation