Presentation on theme: "E.R.G : Measure the electrical responses of various cell types in the retina. Including : The photoreceptors (rods and cones ) Inner retinal cells (bipolar."— Presentation transcript:
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.
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 ํ )
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
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