Abstract
Purpose :
To evaluate the relationship between the pattern electroretinogram (pERG) and the photopic negative response (PhNR) of the flash ERG, both measures of retinal ganglion cell (RGC) function, in patients who have idiopathic intracranial hypertension (IIH).
Methods :
The pERG and PhNR were recorded from 11 IIH patients and 11 age-similar, visually-normal controls. The pERG was recorded in response to a reversing checkerboard pattern that subtended 35° of visual angle. The PhNR, which is a slow negative component that follows the b-wave of the flash ERG, was recorded in response to a long-wavelength flash presented against a short-wavelength adapting field. The PhNR was elicited by both a full-field stimulus (ffPhNR) and a focal macular stimulus (fPhNR) that had an area equivalent to the angular subtense of the pERG checkerboard. PhNR amplitude was measured from baseline and pERG amplitude was measured from the P50 peak to the N95 trough. Additionally, the 24-2 Humphrey visual field mean deviation (HVF MD) was obtained for each patient.
Results :
The ffPhNR, fPhNR and pERG amplitudes were all significantly correlated for the control subjects (all r ≥ 0.84, p ≤ 0.001), but not the IIH patients (all r ≤ 0.54, p ≥ 0.09). The ffPhNR, fPhNR and pERG amplitudes were outside of the normal range in 5, 4, and 3 IIH patients, respectively. On average, the patients had amplitude reductions of the ffPhNR by 35%, fPhNR by 19%, and pERG by 7%. Only the mean ffPhNR amplitude was reduced significantly in the IIH patients compared to controls (p = 0.012). HVF MD was correlated significantly with log fPhNR amplitude (r = 0.76, p = 0.006), but not with log ffPhNR amplitude (r = 0.57, p = 0.07) or log pERG amplitude (r = 0.52, p = 0.10).
Conclusions :
Only the mean amplitude of ffPhNR was reduced significantly in IIH patients compared to controls. This may be because full-field stimuli can capture dysfunction that is localized to the far periphery, which may be overlooked by tests that are restricted to the macula. As such, full-field measures of RGC function, such as the ffPhNR, are well suited for assessing RGC dysfunction in patients who have IIH.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.