E.R.G E.O.G V.E.PE.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 .

OHM’S LAW : V = I . R

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

flash - E.R.GE.R.G pattern - E.R.G multifocal – E.R.G

ISCEV standard for electroretino graphy1. Dark - adapted E.R.G ( rod rospone )2. Dark – adapted E.R.G ( combind rod – cone

response )3. Dark - adapted oscillatory potentials4. Light - adapted E.R.G ( cone response )

5. Light - adapted flicker ( 30 Hz flicker )

Basic technology for E.R.G1.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 2s

- Rod – cone 3 cd/m² cone 30 cd/m² interval

10s

4.Pupillary dilation

5.Pre – exposure to light

E.R.G analysis and reporting amplitude and time to peak

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

Normal ranges for E.R.G Amplitude Implicit Time (μv) (ms)

a-wave photopic 20 – 50 14 - 20 scotopic 190 – 300 20 - 26

b-wave photopic 90 – 180 26 - 34 scotopic 400 – 700 40 - 56

PERG – m E.R.GEvoked by viewing black and white checkeboard or grating function retinal ganglion cell and macula

Amplitude 2 – 8 μm

Peak time 45 – 60 msPN₃₅ - P₅₀ - N₉₅

7.5' v. angleField PERG parafoval

30' v. angle

Glaucoma assessment (30 ํ)

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The electro – Oculogram E.O.G

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 >185Dark adaptation 8 – 10 min

Light adaptaine 8 – 10 min

Limitation in E.O.G

age > 5 years

v. a > 20/200 retard mental

Visual evoked potentialsAn electical signal generated in the occipital region of the cortex in response to visual stimulation Flash V.E.P on set – off setV.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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