Rapid non-mydriatic assessment of panretinal cone system function using a hand-held electroretinography device in ABCA4 retinopathy

Abstract

Purpose : Patients with ABCA4 retinopathy (Stargardt disease) can be grouped by electrophysiology, with prognostic implications: those with a normal photopic full-field electroretinogram (ERG) are less likely to suffer deterioration in generalised retinal function over subsequent years. We used a portable device to obtain photopic ERGs, investigating tolerability, correlation with ultra-widefield autofluorescence (AF) and with prior conventional ERG testing.

Methods : Adults with ABCA4 retinopathy underwent photopic recordings with the portable device (RETeval, LKC Technologies Inc., Gaithersburg, MD, USA) using skin electrodes. Pupils were undilated; the device adjusts stimulus strength according to pupil diameter to deliver a retinal illuminance equivalent to international standards. Right eye recordings were analysed. ERG parameters were compared with control recordings from >500 healthy participants from the TwinsUK cohort. Amplitudes <5^th centile, and peak times >95^th centile were deemed abnormal. Patients underwent ultra-widefield AF (Optos plc, Dunfermline, UK) imaging the same day; images were grouped by presence of far peripheral involvement. The majority of patients had prior conventional ERG testing (in some cases several years previously).

Results : 65 patients were included (mean age 46.4 years; 33 females). Recordings were well-tolerated, lasting <5 min. 40 patients (60%) had peripheral abnormal AF; the proportion of patients with abnormal ERG parameters was higher in these patients (95% vs 23%, p<0.01), and mean ERG b-wave and flicker amplitudes were lower, and peak times more delayed, compared with those without abnormal peripheral AF (p<0.05). Of 32 patients with previously abnormal conventional ERGs, 31 (97%) had abnormal parameters with the hand-held device. Of 24 patients with previous normal ERGs, 18 (75%) had normal hand-held device ERGs.

Conclusions : Recordings were well-tolerated and complete within minutes. The majority (95%) of patients with abnormal far peripheral AF had abnormal ERGs, demonstrating a strong structure-function correlation. Portable ERG findings broadly agreed with prior conventional testing, although the duration between the two tests is likely to mean that in some patients disease progression occurred in the intervening period.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.