Abstract
Purpose: :
The full-field electroretinogram (ffERG) is an emerging tool for detecting and diagnosing retinal dysfunction both in the clinical and laboratory setting. Although it is standard practice to dark adapt human subjects for 20 minutes prior to recording ffERG’s, rodents are typically dark adapted overnight. It has been suggested that rats may require less dark adaptation time to obtain accurate measurements. The purpose of this experiment is to compare the effect of 1 or 3 hr of dark adaptation on ERG amplitude (b-wave, a-b wave, and oscillatory potentials (OP) to those measured after the customary overnight (>12 hr) dark adaptation period.
Methods: :
Brown Norway rats were dark adapted overnight (>12 hours), for 3 hours, or for 1 hour. They were then anesthetized, dilated, and underwent full-field ERG testing using 10-µsec flashes of unattenuated white light (30 cd/mm) with DTL electrodes. The amplitude of b-waves and a-b waves were calculated. Changes in OP amplitude were calculated as a composite of three peaks. Using Student’s t-test and ANOVA analysis, amplitudes obtained after 1 and 3 hours of dark adaptation were compared with those obtained after overnight dark adaptation.
Results: :
The b-wave amplitude after 1 hr (319 ± 6 µV) and after 3 hr (330 ± 14 µV) of dark adaptation was not different than that measured after overnight dark adaptation (332 ± 15 µV, p=0.74, n=6). Similarly, the a-b wave amplitude after 1 hr and 3 hr (449 ± 7 µV and 454 ± 20 µV respectively) was not different from overnight adaptation (448 ± 26 µV, p=0.99, n=6). The composite sum of OPs after overnight dark adaptation was 449 ± 6 µV, which was not different from amplitudes after 1 hr or 3 hr of dark adaptation (415 ± 8 µV and 415 ± 18 µV, respectively, p=0.48, n=6).
Conclusions: :
ffERG performed after 1 hr and 3 hr of dark adaptation showed no difference in amplitudes of b-waves, a-b waves, or OPs when compared to the customary overnight dark adaptation. This indicates that less time is required to prepare brown Norway rats for experimental ERG studies while still obtaining consistent readings.Supported in part by the Richmond Eye and Ear Foundation and the Commonwealth Health Research Board.
Keywords: electroretinography: non-clinical • photoreceptors: visual performance • contrast sensitivity