Test–retest reliability of scotopic full-field electroretinograms in rabbits
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To explore test–retest reliability of standard scotopic full-field ERG measurements in New Zealand White rabbits. The ERG is widely used for testing of retinal integrity after any ocular treatment. We here present detailed stimulus–response dependencies for single healthy and untreated animals, concentrating on test–retest reproducibility.
Materials and methods
Five New Zealand White rabbits (aged 8–10 weeks, weight about 2.0–2.5 kg) underwent binocular ERG measurements after intramuscular anesthesia and pharmaceutical pupillary dilatation at a baseline day and 10 days later. Eleven scotopic flash strengths (0.0001–10 cd s/m2) were presented. Variability was quantified via the 95% limits of agreement (LOA).
The a-waves displayed the typical monotonic sigmoid amplitude increase with flash strength, and the b-waves peaked at 0.01 cd s/m2, followed by a marked dip at 0.1–0.3 cd s/m2. LOA of both waves went through a maximum in the dip region. LOA divided by mean amplitudes (relative LOA) was fairly flat over flash strength, around 20% beyond the dip. Intraindividual interocular variability was markedly lower, around 10%.
Scotopic ERG responses in rabbits display a region of high variability at 0.1–0.3 cd s/m2; beyond that region the amplitude-LOA is 20%, the interocular LOA being half that value. The use of intraindividual control eyes for testing any toxicity of ocular agents thus appears markedly more sensitive. As a rule of thumb, we found the relative 95% LOA as 33% between individuals, 20% across sessions and 10% between eyes.
KeywordsERG Rabbits Test–retest reliability
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