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Talha Soorma, Ibtesham Hossain, Ibrahim Sheriff, Noor Hassan, Diana Kozareva, Ekaterina Yonova, Yemi Adelaja, Miles Stanford, Katie M Williams, Christopher J Hammond, Omar Abdul Rahman Mahroo; Normative parameters for rapid photopic electroretinogram recordings with a hand-held device: results from over 500 subjects. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4889.
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© ARVO (1962-2015); The Authors (2016-present)
The RETeval system (LKC Technologies Inc., Gaithersburg, MD, USA) is a hand-held device for eliciting and recording electroretinograms (ERGs) with skin electrodes. The device holds promise in facilitating rapid screening assessments of retinal function. In this study, we recorded photopic ERGs in several hundred volunteers to establish some normative values.
Subjects were recruited over 14 months from the TwinsUK cohort at St Thomas’ Hospital in London. Photopic ERGs were recorded from subjects in light-adapted conditions (standard room light). Pupils were not pharmacologically dilated, but stimulus intensities were adjusted by the device according to pupil area to deliver retinal iluminances corresponding to international standards. Skin electrodes were applied without cleaning the skin to minimise delay. Flash stimuli were delivered first and then flicker stimuli; the right eye was stimulated first then the left. Parameters were averaged from both eyes where recordings from both eyes were available. Right and left eyes were compared where recordings from both eyes were available (paired t test).
Over the study period, 558 participants underwent recordings (84% female; 90% white ethnicity). Mean (SD) age was 50.0 (17.0) years. Mean (SD) amplitudes were -7.8 (9.3), 30.0 (13.0) and 30.8 (9.9) microvolts for photopic flash a-wave, b-wave and flicker responses respectively (5th centile values were -1.8, 13.3 and 16.6 microvolts respectively). Mean (SD) implicit times for these parameters were 12.1 (2.9), 28.7 (2.1) and 25.6 (1.5) ms respectively (95th centile values were 17.2, 31.1 and 27.8 ms). Statistically significant inter-eye differences (p<0.01) were found for flicker amplitudes and implicit times, and flash a-wave and b-wave amplitudes: right eye flicker responses were on average 3.9 microvolts larger, and 0.2 ms faster than left eye responses; right a-waves and b-waves were on average 1.2 and 3.7 microvolts larger respectively.
This study provides normative data for the handheld device from a large cohort, with cut-off values that may be useful for studies in patients. These values differ from those obtained with other methods of recording. Interesting right-left differences were found, which might relate to electrode position or to adaptive effects as the eyes are recorded from sequentially.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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