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ELECTRORETINOGRAPHY
Dr Frank FAMOSE
DVM, CES Ophtalmologie
Ekaterinburg May 2010
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
c c
a-wave : receptor level Other waves :
b-wave : post-receptor level Oscillatory potentials (OP)
c-wave : pre-receptor level 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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Electroretinography material
►Collecting and
recording data
 Amplification
 Filtration
 Computer
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Variations in components of ERG :
photoreceptors
►Rods ►Cones
 Low light intensity  High light intensity
 Low frequency  High frequency (>30Hz)
 Rhodopsine  2 spectral sensitivities
 Saturation process  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 ►Photopic conditions
(darkness) (daylight conditions)
 Rods in dim flash  Saturation of rods
 Cones in strong flash  Specific stimulation
stimulation of cones
Dim flash of blue light Strong flash of achromatic light
in darkness conditions in darkness conditions
Stimulation of rods only Saturation of rods
Specific 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 Rods stimulation
►Photopic stimulation in
photopic conditions Rods and cones
►Photopic stimulation in stimulation
30 hz frequency Cones stimulation
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ERG protocols : coloured
stimulations
►Darkness adaptation
(20 min)
►Dim blue stimulation in
scotopic conditions Rods stimulation
►Photopic red stimulation in
photopic conditions Cones stimulation
►Photopic white stimulation
in 30 hz frequency Cones stimulation
ERG protocols : « mix » protocol
►Room light adaptation
(2 hours)
►Photopic white
stimulation Cones stimulation
►Darkness adaptation
(20 min)
►Scotopic blue Rods stimulation
stimulation in darkness
►Photopic stimulation in
30 hz frequency 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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ERG analysis
One month later…
Clinical indications of ERG
►Preoperative ►Clinical evaluation of
evaluation of retina retina in pathologic
(cataract surgery) conditions
►Amaurosis ►Early diagnosis of
retinal conditions
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Conclusion
►Fonctionnal evaluation of global retinal
activity
►Numerous factors of variation
►Needs pratice and standardisation
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