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The Test-Retest Reliability of the Photopic Negative Response (PhNR)

The Test-Retest Reliability of the Photopic Negative Response (PhNR)

Jessica Tang, Thomas Edwards, Jonathan G Crowston, Marc Sarossy

Transl Vis Sci Technol. 2014 Nov 3;3(6):1.

PMID: 25374770

Abstract:

Purpose:
The photopic negative response (PhNR) may be useful as a tool to monitor longitudinal change in retinal ganglion cell (RGC) function. The goal was to assess PhNR test-retest reliability, and to estimate the amount of change between tests that is likely to be statistically significant for an individual test subject.
Methods:
Photopic electroretinograms (ERGs) were recorded from 49 visually normal subjects (mean age, 38.9 years; range, 21-72 years). Signals were acquired using Dawson-Trick-Litzkow (DTL) electrodes in response to red stimulus at four flash energies (0.5, 1, 2.25, 3 cd·s/m2) on a blue background (10 cd/m2). The PhNR amplitude was recorded from prestimulus baseline to trough (BT), prestimulus baseline to fixed time point (BF), and b-wave peak to trough (PT). The ratio of baseline PhNR to b-wave amplitude (BT/b-wave) was calculated. Reliability was assessed using the intraclass correlation coefficient (ICC2,1) and coefficient of repeatability (CoR).
Results:
Flash energy of 1.00 cd·s/m2 produced reliable, well-defined traces. At this stimulus, the a- and b-wave amplitudes were reproduced with moderate reliability (ICC, 0.62; CoR%, 90.0%; and ICC, 0.74; CoR%, 54.3%; respectively). For PhNR, the order from most to least reliable measurement was: PT (ICC, 0.64; CoR%, 59.1%), BT (ICC, 0.40; CoR%, 148.3%), and BF (ICC, 0.22; CoR%, 166.1%). The BT/b-wave did not improve reliability (ICC, 0.37; CoR%, 181.5).
Conclusion:
The b-wave peak-to-PhNR trough amplitude produced the most reliable measurement.
Translational relevance:
A relatively large magnitude of change in PhNR amplitude is required to make clinical inferences about changes in RGC function. Refinement to the technique of acquisition and/or processing of the PhNR is recommended to improve reliability.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
IAR42152	Flash Point - PT			Price

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