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Huy Nguyen, Radouil T Tzekov; Full-field ERG signal can uncover photic blink reflex signature.. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2509.
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© ARVO (1962-2015); The Authors (2016-present)
The photic blink reflex (PBR) can be a sign of photophobia, a symptom associated with a variety of retinal and eye diseases. We used full-field ERG to extract the underlying EMG signals to explore the occurrence and timing of PBR in clinical settings.
This was a retrospective observational study of patients with various clinical diagnoses who underwent ERG testing between 1/2015 and 1/2017 at USF Eye Institute in Tampa. Recordings based on dark-adapted 3 oscillatory potentials (OPs), as part of standard ISCEV protocol, were analyzed. Patients age 18+ with recordable dark-adapted ERG were included. Aberrant recordings >2σ from mean RMS signals were excluded. The UTAS E3000 (LKC Technologies) was used for stimulus generation (white xenon flash at 3.0 cd.s/m2) and recording (bandpass 75-500 Hz), while DTL electrodes were used as active. Recordings were exported and analyzed with Matlab.
56 eyes (28 patients) generated 9 raw signals per eye. 12 male and 16 females, age 50.9 +/- 17.6 (range 18-79). OP activity, PBR, and muscle-dominated activity was present in 50 eyes from 26 patients, 43 eyes from 24 patients, and 34 eyes from 18 patients, respectively. 16 eyes from 12 patients had unpaired OP and PBR. OP signal after photic stimulus was clearly observable and began at 0-5 ms with duration of 41.7 +/- 6.7 ms with its RMS having an area under the curve (RMS-AUC) of 50-350 ms*µV2, corresponding to the well-known and anticipated retinal response. Photic blink reflex (PBR) signal began at 53.4 +/- 13.4 ms with duration of 51.7 +/- 24.5 ms with AUC-RMS 25-450 ms*µV2. We also observed a later muscle-dominated activity at 124.1 +/- 19.0 ms where voluntary blink response would be difficult to distinguish from reflexive muscle activity. Right/left eye varied in terms of OP duration at 9 +/- 12%, PBR start at 14 +/- 13%, PBR duration at 25 +/- 24%, and start of muscle dominant activity at 8 +/- 10%.
Isolated EMG data from full-field ERG recordings contained a consistent electrical peak representative of an eyelid response (PBR) not shown in processed ERG data. This PBR had variable duration but occurred precisely after the OP response and before the late blink reflex. PBR at times occurred without retinal activity and retinal activity without PBR. Studies are ongoing to further quantify the relationship between the muscle signal in the ERG and associated eyelid activity.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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