All You Ever Wanted to Know About ERG but Were Afraid to Ask American Academy of Ophthalmology, Orlando, 2002 10 November 2018

Testing Levels of the Visual System clinical neurophysiology allows assessment of retina, optic nerve, chiasm, and retrochiasmal visual pathways the ERG can functionally dissect the neural retina 10 November 2018

Electroretinogram (ERG) ERGs are mass electrical activity from the retina in response to visual stimulation the ERG is objective, non-invasive measure of electroretinal function OD OS a b 100 Uv 25 ms 10 November 2018

Recording the ERG Photic stimulator Plotter electrode

Microconductive Thread ERG Electrodes Contact Lens Electrode Microconductive Thread Electrode 10 November 2018

Modern ERG Recording Electrodes DTL-Plus™ Microconductive Thread Electrode 10 November 2018

ERG Electrodes Microconductive thread electrode neglible mass convenient to use, disposable no interference with pupil or optics reliable ERG recordings well tolerated by children Microconductive thread electrode 10 November 2018

Pre-Millenium ERG Technology Ganzfeld Stimulation (full-field) provided by xenon flash photostimulator full visual field stimulation stimulus intensity stimulus wavelength variable stimulus rate variable background intensity 10 November 2018

Modern ERG Stimulator 10 November 2018

Mini-Ganzfeld LED Stimulator 4.5 inch diameter 176 LEDs “blue” (470 nm) “green” (525 nm) “red” (640 nm) 7 log unit luminance range optoelectronic stimulation can be more precisely controlled and calibrated than xenon discharge tubes Espion Colorburst™ 10 November 2018

Components of the Flash ERG 11/10/2018 Components of the Flash ERG b-wave Implicit time (i.t.)= time from stimulus until peak of activity b i.t. Amplitude (amp)= voltage magnitude at peak of activity b amp a amp a i.t. a-wave

Generator Sites of the Flash ERG a-wave originates from the photoreceptor layer b-wave is a glial potential originating from the Müller cell and the bipolar cells OPs originate from amacrine cells flash ERG reflects electroretinal activity distal to the ganglion cell layer 10 November 2018

Oscillatory Potentials (OP) OD OS 5 Uv 15 ms a subcomponent of the ERG seen on ascending limb of the b-wave Wachtmeister (1977) demonstrated OPs originate from amacrine cells in the inner plexiform layer 10 November 2018

Rod vs Cone ERGs Rod ERG OPs Cone ERG 30 Hz Flicker 10 November 2018

Pattern ERG (PERG) Elicited to pattern stimulation (usually checkerboard or bar gratings) much lower amplitude than flash ERGs fixation is critical for PERG, not flash ERG PERG reflects activity in the ganglion cell layer 10 November 2018

Generators of the Pattern ERG PERGs are generated in the ganglion cell layer PERGs may reflect both activation of cell body and axonal activity 10 November 2018

ISCEV ERG Standards International Society for Clinical Electrophysiology of Vision (ISCEV) ERG standard established in 1989 standards for 5 commonly obtained responses ERG developed by the rods (dark-adapted) maximal ERG response (dark-adapted) Oscillatory Potentials ERG developed by the cones (light-adapted) ERG to flicker 10 November 2018

Who are the Clients of an Electrodiagnostic Service? Patients whose eyes have: symptoms suggestive of known neurological or ophthalmological disease unexplained visual loss medico-legal problems workman’s compensation defects associated with psychiatric disturbance, mental or physical handicap pediatric neuro-ophthalmic practice metabolic, hereditary or neurological disease with visual impairment non-seeing child 10 November 2018

Who are the Clients of an Electrodiagnostic Service? Patients with media opacities prior to corneal grafting or cataract surgery vitreous hemorrhage (in DR or following trauma, RD) Patients with uveitis or inflammatory eye disease Patients with suspected disease or carrier status of inherited visual disorders Patients requiring quantitative assessment of disease progression Assessment of retinal and optic nerve function following trauma 10 November 2018

Indications for ERG aid to diagnosis in patients suspected of having stationary or progressive inherited retinal degenerations to rule out clinically unaffected family members to evaluate possible female carriers of x-linked disease to assess patients with retinal toxicity due to metallosis (siderosis) retinotoxic or neurotoxic medications chloroquine, Hydroxychloroquine, ethambutol, phenothiazine Desferrioxamine, Tamoxifen Vigabatrin toxicity? patients with OHT/glaucoma to identify eyes that are likely to develop neovascularization in diseases such as CRVO and DR documenting therapeutic effects of surgery or medication 10 November 2018

Electrodiagnostics of the Future Standardized instrumentation Standardized testing protocols Multicenter normative data collection Web-based telemedicine application University of Ottawa Eye Institute announces ERG Reading Centre 10 November 2018