Abstract
Purpose :
The Burian-Allen (B-A) contact lens electrode and the DTL fiber electrode (invented in 1954 and 1979, respectively) are the most frequently used electrodes in the US for recording the electroretinogram (ERG), but each present challenges with regard to convenience, safety and/or signal quality. A new design for an ERG electrode (RM) that overcomes many of the limitations of the B-A and DTL electrodes was developed (Fig. 1A-C) and compared to the older designs for signal quality, comfort and ease of use.
Methods :
A soft silicone electrode substrate was designed to closely conform to the anterior surface of the eye and position a ring-shaped electrode outside the margin of a dilated pupil. The electrode is recessed within a channel and makes electrical contact via the tear film. The substrate extends beneath the eyelids for stability, and is shaped to prevent blinking. The three electrode styles were compared using full-field flash stimuli in a dark-adapted healthy subject. Responses were evaluated for pre-stimulus noise, a- and b-wave amplitudes, and repeated-measure variability.
Results :
Mean a-wave amplitudes (+/-1 SD) were significantly larger with the RM electrode (198+/-13 uV) compared to the B-A electrode (92+/-3 uV) and the DTL electrode (145+/-13 uV); similar results were obtained for b-wave amplitudes. The B-A reference electrode picks up a measurable ERG signal, which is then subtracted from the signal recorded at the corneal electrode by differential amplifiers. A-wave amplitudes for repeated stimuli were most consistent with the B-A electrode, and least consistent with the DTL electrode (standard deviation as % of mean: 4% for B-A, 7% for RM, 9% for DTL). Both DTL and B-A electrodes had significant baseline drift (+/-200 uV) compared to the RM design (+/-50 uV). The RM design was more comfortable and less imposing during installation than the B-A but comparable to the DTL.
Conclusions :
The greater signal to noise ratio and lower baseline drift observed with the RM electrode design is attributed to the increased stability on the eye, optimum corneal contact and reference electrode location. These advantages are obtained in a soft, disposable design, increasing patient comfort and safety.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.