Towards rapid assessment of retinal function in clinic: comparison of implicit times of photopic flicker electroretinogram responses recorded using a conventional and a portable system in patients with Birdshot chorioretinopathy

Purpose : Birdshot chorioretinopathy (BCR) is a chronic inflammatory disease which follows a variable course. Disease activity can be difficult to assess objectively. The implicit time of the 30 Hz photopic flicker electroretinogram (ERG) has been shown to be a sensitive parameter in these patients. Electroretinography is not universally available, limiting its utility in guiding treatment decisions in many settings. A portable device allowing rapid measurements in clinic could be transformational in this regard, but such devices require validation. Methods : A hand-held device with skin electrodes (RETeval, LKC Technologies, Inc., Gaithersburg, MD, USA) and a more conventional full-field device with a conductive fibre recording electrode (Diagnosys ColorDome, Diagnosys, Lowell, MA, USA) were used to record photopic flicker ERGs in Birdshot patients attending a single eye service. For portable recordings, pupils were undilated (stimuli aimed to deliver similar retinal illuminances to international standard stimuli); pupils were dilated for conventional recordings. Implicit times were compared. Also, recordings made from over 300 healthy subjects provided control data. Results : Recordings were made from 11 patients (21 eyes). Mean (SD) age was 60.9 (7.5) years. Implicit times ranged from 24.4 to 35.2 ms and from 24.5 to 37 ms for portable and conventional devices respectively. Mean (SD) implicit times were 29.1 (3.7) ms and 30.3 (4.2) ms respectively. Implicit times were slightly but significantly shorter with the hand-held device (p =0.0003). The correlation coefficient between the devices was 0.96 overall (0.98 and 0.96 for right and left eye recordings). Using the control data from healthy subjects, upper cut-off values (mean plus 2SD) of 28.6 ms and 29.1 ms were set for the two devices for designating times as “prolonged”. Agreement was quantified with a kappa of 0.81 (95% CI, 0.56 to 1.0) Conclusions : Although implicit times differ between the two systems, highlighting the importance of control data, the correlation is extremely high, with very strong agreement. The portable device holds promise in providing reliable flicker time measurements, undilated, within minutes potentially at every clinic visit. This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016. ; ; ; ;