e.r.g : measure the electrical responses of various cell types in the retina. including : the...
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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 .
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OHM’S LAW : V = I . R
Resistance including : fluid in the extracellular spaces of the retina – vitreous – lens aqueous - cornea
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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 )
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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
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E.R.G analysis and reporting amplitude and time to peak
a - wave b - wave c - wave d - wave
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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
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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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2 810فیلم
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2 16فیلم
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809فیلم
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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
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Limitation in E.O.G
age > 5 years
v. a > 20/200 retard mental
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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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3 17فیلم
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Thanks