Abstract
Purpose :
ISCEV Standards specify 20 minutes of dark adaptation (DA) before the recording of rod-dominated electroretinograms (ERGs). Having a patient occupy a completely dark room for this time is inconvenient for the patient and costly for the practice; therefore, rod ERG testing is often avoided. We tested two alternatives to ease rod function testing: the wearing of red adaptation goggles (commonly used in amateur astronomy) in lieu of sitting in a dark room, and dark adapting for 10 minutes instead of 20.
Methods :
Healthy volunteers had scotopic ERGs recorded in 4 conditions: 10 and 20 minutes of DA, where the DA was done in a dark room (DR) or in a normally-illuminated office environment while wearing red-tinted goggles (RG) (Orion 5942 AstroGoggles). ERGs were recorded using the RETeval device and Sensor strip electrodes (LKC Technologies). Subjects were not dilated and the Troland equivalent of the ISCEV standard scotopic protocol was followed (DA0.01, DA3, DA10). Subjects were light adapted for at least 10 minutes between trials. Amplitudes and implicit times of a-waves and b-waves were measured and statistically assessed with two-way ANOVA and Tukey’s multiple comparison test with a 0.05 level of significance (Prism, GraphPad, Inc.).
Results :
Five females (age 41±14) and 5 males (age 43±18) were tested. Amplitudes: No significant differences were obtained between any of the 4 conditions. Implicit times: No significant differences were noted between the DR and RG methods for DA0.01 b-wave time and any of the a-wave times. The b-wave times were quicker in RG than in DR for DA3 and DA10 by an average of 6 ms (p=0.02) and 5 ms (p=0.008) with 20 min DA time and by an average of 6 ms (p=0.02) and 8 ms (p=0.001) with the 10 min DA time, respectively. No significant differences were measured between the right and left eye at any of the tests for amplitudes or implicit times, although the RETeval device tests the right eye prior to the left eye.
Conclusions :
These results suggest that red goggles and 10 minutes of DA time can be used to obtain clinically meaningful assessment of rod function, as none of the amplitudes were statistically different. Dark adaptation via RG did produce shorter implicit times, likely an effect from the L-cones that weren’t dark adapted; however, clinical rod functional assessment is less dependent on timing than amplitude.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.