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David Drucker, Gonzalo Ortiz, Connor Hyde, Joseph Staffetti, Radouil T Tzekov; Full-field ERG i-wave parameters in patients with retinal degenerations. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5016.
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© ARVO (1962-2015); The Authors (2016-present)
The i-wave is a positive deflection on the photopic full-field ERG response that occurs roughly 50ms after the onset of a stimulus and 20ms after the peak of the clinically-relevant b-wave. The electrophysiological mechanisms underlying the i-wave are thought to predominantly originate from retinal ganglion cell (RGC) activity though to date, there has been little attempt to characterize this I-wave and as such, conveys little clinical value. The goal of this retrospective study was to analyze the i-wave in a diverse clinical population.
The full-field single flash photopic ERG (Photopic 3.0 ERG according to ISCEV standard) recordings of 97 patients (35 M; 62 F; age range 19.2 - 80.2 years; 187 eyes) with a variety of clinical diagnoses, but mostly having or being suspected to have retinal degenerations, were analyzed and the i-wave amplitude (measured from the preceding peak) was determined together with the peak time. These parameters were correlated with the other two major photopic ERG components (a-and b-wave) and with age.
In this patient population, an i-wave was recordable in 96% of the cases when both a- and b-wave were recordable too. The interocular correlation was 0.643 for amplitude and 0.830 for peak time. Our analysis showed a moderate correlation between i-wave amplitude and and both a- and b-wave amplitudes (0.418 and 0.546, respectively). The correlation was similar for i-wave peak time vs. a-wave peak time (0.485), but was stronger with b-wave peak time (0.758). Further analysis showed that i-wave amplitude was not influenced by age (slope not different from 0; p=0.429), but peak time was (0.8 msec increase/decade; p=0.03) and these results were different compared to the correlations of b-wave with age.
There might be additional diagnostic utility of the i-wave in the clinical full-field ERG beyond the standard information gleaned from a- and b-wave analysis in patients with (or suspected for) retinal degenerations and further studies in this regards are warranted.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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