Abstract
Purpose :
The photopic negative response (PhNR) is a late component of the light-adapted electroretinogram (ERG), and derives from retinal ganglion cells. We recorded PhNRs from idiopathic intracranial hypertension (IIH) patients and explored associations with severity.
Methods :
ERGs were recorded, following mydriasis and exposure to room light, using conductive fibre electrodes with a portable device (RETeval, LKC technologies, MD USA). Red flashes (1.0 cd.s/m2) were delivered, at 3.4 Hz, on a 10 cd.s/m2 blue background (averages from 400 flash presentations). The device software gave PhNR amplitudes (at 72 ms or as a ratio to b-wave). ERGs were assessed for drift, noise and reproducibility. The eye with a better quality trace was chosen for PhNR analysis; if both were equally good, the eye with poorer visual field function was chosen. IIH severity was determined using optical coherence tomography-derived retinal nerve fibre layer (RNFL) thickness and Modified Frisen scale (MFS): mild (MFS1-2), severe (MFS≥3, RNFL thickness>150, or atrophic) or in remission (resolved with no atrophy). Patients without papilloedema deemed not to have IIH or any other eye conditions act as controls. P72 and p-ratio were compared in the four groups (Kruskal-Wallis), with each group also compared to control (Mann-Whitney).
Results :
Of 99 patients, 86 (7 control, 79 IIH) were included; 13 were excluded (9 poor quality ERG, 4 alternative diagnosis). 91% of IIH patients were female; median (IQR) age was 33 (27-39), BMI 34.8 (30.4-40.0). 86% of controls were female; median (IQR) age was 52 (31-64), BMI 34.5 (32.3-42.2). P72 and p-ratio differed significantly across groups with a trend towards smaller PhNR amplitudes in more severe IIH, p=0.0417 and p=0.0389 respectively. Largest differences were observed between severe IIH and controls (median P72: -3.4 vs. -7.1, p=0.0096, and median p-ratio: 0.12 vs. 0.23, p=0.0073). Comparing severe and mild IIH groups, p-ratio differed significantly (0.12 vs. 0.17, p=0.014), but not P72 (-3.4 vs. -6.0, p=0.064). Patients in remission and controls exhibited non-significant differences (median P72: -5.0 vs. -7.1, p=0.19, and median p-ratio: 0.18 vs. 0.23, p=0.48).
Conclusions :
We found associations between PhNR parameters and disease severity in a large IIH cohort. The PhNR could potentially provide additional assessment of disease severity in these patients.
This is a 2021 ARVO Annual Meeting abstract.