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Photopic Negative ERG (PhNR)

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Photopic Negative ERG (PhNR)

Posted on Friday April 1, 2022

A Photopic Negative Response (PhNR) is a test of generalized retinal ganglion cell health and function. Reduced PhNR amplitudes might be indicators for: glaucoma, optic atrophy, central retinal artery occlusion, ischemic optic neuropathy, diabetic retinopathy, or idiopathic intracranial hypertension.  


This protocol uses a low intensity red flash on a rod-saturating blue background. It can be done binocularly with ColorDome, or monocularly with ColorFlash or ColorBurst stimulators. The protocol has two steps: a 1Hz ISCEV standard or a 4Hz that may reduce eye twitching in some people.  


The a- and b-wave responses are similar to a standard white-light ERG. While the PhNR ganglion cell response trails behind the a- and b-wave photoreceptor and bipolar cell responses, respectively.  


Example Test

Photopic Negative (PhNR) Response



Frishman, L., Sustar, M., Kremers, J. et al. ISCEV extended protocol for the photopic negative response (PhNR) of the full-field electroretinogram. Doc Ophthalmol 136, 207–211 (2018). https://doi.org/10.1007/s10633-018-9638-x