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Purpose : The RETeval system (LKC Technologies, Inc., Gaithersburg, MD, USA) is a hand-held device for recording electroretinogram (ERG) responses with skin electrodes, placed over the lower eyelid, close to the lid margin. Some subjects find this uncomfortable due to proximity to eyelashes. We explored the effect of changing electrode position in healthy subjects. Methods : Photopic flicker ERGs were recorded in 120 healthy twins as part of a wider study. For 48 subjects (Group 1), recording electrodes were placed in “comfortable” positions, even if this was 1-2 cm below the lid margin. For 72 subjects (Group 2), the lid margin position was used as recommended by the manufacturer. Photopic flicker and flash ERGs were recorded for an additional 5 healthy subjects in two consecutive recording sessions: in the test eye, the electrode was placed just below the lid margin in the first session, and 1.5 cm below in the second; in the fellow eye (control eye), the electrode was just below the lid margin throughout. Amplitudes and implicit times (test eye normalised to control eye) were compared for the two sessions. Pupils were undilated; stimuli were designed to deliver the same retinal illuminance as international standard stimuli. Results : For Group 1, mean (SD) flicker ERG amplitudes were 22.9 (13.1) and 22.4 (13.3) µV for right and left eye respectively. Implicit times were 25.8 (2.1) and 25.9 (1.1) ms. For subjects with consistent positioning at the lid margin, amplitudes were 35.3 (10.1) and 37.6 (17.3) µV; implicit times were 25.3 (1.1) and 26.1 (2.4) ms. Mean amplitudes were significantly lower for the first group (p<0.0001), but implicit times did not differ (p>0.2). For the subjects in whom electrode position was changed between recording sessions, flash and flicker amplitudes were significantly smaller when positioned 1.5 cm from the lid margin (p<0.05), but implicit times were similar (p>0.6). Conclusions : Moving RETeval electrodes further from the lid margi

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, hig

Purpose : The RETeval system (LKC Technologies, Inc., Gaithersburg, MD, USA) is a hand-held device for recording electroretinogram (ERG) responses with skin electrodes, placed over the lower eyelid, close to the lid margin. Some subjects find this uncomfortable due to proximity to eyelashes. We explored the effect of changing electrode position in healthy subjects. Methods : Photopic flicker ERGs were recorded in 120 healthy twins as part of a wider study. For 48 subjects (Group 1), recording electrodes were placed in “comfortable” positions, even if this was 1-2 cm below the lid margin. For 72 subjects (Group 2), the lid margin position was used as recommended by the manufacturer. Photopic flicker and flash ERGs were recorded for an additional 5 healthy subjects in two consecutive recording sessions: in the test eye, the electrode was placed just below the lid margin in the first session, and 1.5 cm below in the second; in the fellow eye (control eye), the electrode was just below the lid margin throughout. Amplitudes and implicit times (test eye normalised to control eye) were compared for the two sessions. Pupils were undilated; stimuli were designed to deliver the same retinal illuminance as international standard stimuli. Results : For Group 1, mean (SD) flicker ERG amplitudes were 22.9 (13.1) and 22.4 (13.3) µV for right and left eye respectively. Implicit times were 25.8 (2.1) and 25.9 (1.1) ms. For subjects with consistent positioning at the lid margin, amplitudes were 35.3 (10.1) and 37.6 (17.3) µV; implicit times were 25.3 (1.1) and 26.1 (2.4) ms. Mean amplitudes were significantly lower for the first group (p<0.0001), but implicit times did not differ (p>0.2). For the subjects in whom electrode position was changed between recording sessions, flash and flicker amplitudes were significantly smaller when positioned 1.5 cm from the lid margin (p<0.05), but implicit times were similar (p>0.6). Conclusions : Moving RETeval electrodes further from the lid margi

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, hig