PhNR Repeatability Project
Research type
Research Study
Full title
A study investigating the feasibility of measuring photopic negative response (PhNR) in normal volunteer participants and its repeatability
IRAS ID
174106
Contact name
James Wolffsohn
Contact email
Sponsor organisation
Aston University
Duration of Study in the UK
0 years, 6 months, 0 days
Research summary
The objective of this study is to establish and assess the feasibility of a protocol to record the photopic negative response in visually normal volunteer participants. The electroretinogram (ERG) is an objective electrophysiological test to determine the function of the light sensitive layer of the eye (the retina).
Electroretinogram (ERG) recording involves recording the small electrical signals from the eye in response to a flashing light. These signals are recorded by small contact stickers that are placed on the face, on the temples, forehead and under the eyes.
ERGs may be performed when the person is adapted to the light or adapted to the dark. The standard light-adapted, or “photopic” ERG has 2 distinct waveforms: a negative a-wave and positive b-wave.
The photopic negative response (PhNR) is a slow, negative wave that follows the second wave of the full-field ERG.Recent studies have shown that the PhNR is selectively reduced in diseases of the retinal ganglion cells and optic nerve, such as glaucoma and optic atrophy. Retinal ganglion cells travel to the back of the eye to form the optic nerve which sends electrical messages from the eye to the brain to allow us to see. Glaucoma is a group of eye disorders which cause damage to the optic nerve.
The photopic negative response is a way of measuring how well certain cells at the back of the eye function, and could be used to tell us if a patient is in the early stages of glaucoma or other neural retina disease.
As the PhNR shows promise for assessment of retinal ganglion cell function, and therefore glaucoma, its reliability at repeating such measurements must be assessed. Inter-session reliability, the consistency of results between sessions, determines the confidence with which we can distinguish clinically significant results from inherent measurement variability. Inherent measurement variability is the expected amount of change in test results per session, which should be small.
This is a repeatability study investigating the inter-session and inter-ocular (between eyes) variability of the PhNR in visually normal volunteers. The PhNR will be measured by measuring the participant's electroretinogram (ERG) response to flashing light. The PhNR of the participant will be measured 4 times to determine its repeatability.
REC name
London - Queen Square Research Ethics Committee
REC reference
15/LO/1869
Date of REC Opinion
23 Oct 2015
REC opinion
Favourable Opinion