Abstract
Purpose :
This study evaluated the performance of two corneal electroretinogram (ERG) sensors when used with a hand-held ERG system. Conductive thread-type sensors (DTL Plus, Diagnosys LLC) and prototype disposable contact lens sensors (RM Electrode, provided by RetMap Inc.) were used. The hypotheses were that the RM sensor, which makes electrical contact with the cornea only, would provide signals of higher signal to noise ratio (SNR) and improved repeatability (responses within a test, and across repeated tests) when compared to the DTL sensor, which makes electrical contact with the cornea and other nearby tissues.
Methods :
Three normally-sighted subjects (six eyes) participated. Following administration of a corneal numbing agent the DTL was installed in one eye and the RM in the other eye (randomly assigned). Using the handheld RETeval system (LKC Technologies) the “ISCEV 6 Step Dark First Td” protocol (no pupil dilation) was followed, with 10 min dark- and light-adaptation periods. After the protocol was complete the sensors were removed, new sensors of the opposite type were installed in each eye, and the protocol was repeated. The entire procedure was carried out on two consecutive days. Repeatability was quantified as the root mean squared error (RMSE) over a 150 ms post-stimulus interval. RMSE was calculated between responses to repeated stimuli within a test, and between averaged waveforms obtained in tests performed on consecutive days.
Results :
For the 3.0 dark-adapted stimulus (85 Troland seconds), RMSE values for repeated tests were lower in 67% of eyes with the RM sensor, with an average reduction of 40% compared to values obtained with DTL sensors. RMSE values for repeated stimuli within a test were lower in 100% of eyes with the RM sensor, with an average reduction of 59% compared to values obtained with DTL sensors. SNR values for individual responses in eyes with the RM sensor were increased by 128% (4.28 dB), on average, compared to values obtained with DTL sensors.
Conclusions :
A disposable sensor designed to improve the consistency and location of corneal contact (RM) can improve repeatability of responses compared to thread-type ERG sensors. Improved repeatability has the potential to shorten ERG test times and narrow reference ranges used for diagnosis and monitoring.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.