E.R.G : Measure the electrical responses of various cell types in the retina. Including : The photoreceptors (rods and cones ) Inner retinal cells (bipolar and amacrine cells) ganglion cells.

Resistance including : fluid in the extracellular spaces of the retina – vitreous – lens aqueous - cornea

ISCEV standard for electroretino graphy 1. Dark - adapted E.R.G ( rod rospone ) 2. Dark – adapted E.R.G ( combind rod – cone response ) 3. Dark - adapted oscillatory potentials 4. Light - adapted E.R.G ( cone response ) 5. Light - adapted flicker ( 30 Hz flicker )

1. Dark adaptation( 20 min) – light adaptation( 10 min) Hard CL 2. Electrodes DTL Foil 3. Stimulation and duration - Rod 0.01 cd/m² = 2.5 log units interval 2 s - Rod – cone 3 cd/m² cone 30 cd/m² interval 10 s 4. Pupillary dilation 5. Pre – exposure to light

a - wave b - wave c - wave d - wave

Amplitude Implicit Time (μv) (ms) a-wave photopic 20 – scotopic 190 – b-wave photopic 90 – scotopic 400 –

Evoked by viewing black and white checkeboard or grating function retinal ganglion cell and macula Amplitude 2 – 8 μm Peak time 45 – 60 ms PN ₃₅ - P ₅₀ - N ₉₅ 7.5' v. angle Field PERG parafoval 30' v. angle Glaucoma assessment ( 30 ํ )

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Function of the outer retina and retinal pigment epithelium in which the change in the electrical potential between the cornea and the ocular fundus is recorded during successive periods of dark and light adaptation E.O.G Arden ratio = LP/DT 165 – 185 % Normal range >185 Dark adaptation 8 – 10 min Light adaptaine 8 – 10 min

age > 5 years v. a > 20/200 retard mental

An electical signal generated in the occipital region of the cortex in response to visual stimulation Flash V.E.P on set – off set V.E.P Pattern V.E.P Sweep V.E.P reversal Clinical application for the V.E.P - Determination of refractive Error - Visual acuity in infancy cortical blindness

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