Full Field ERG in Albino and Pigmented Rabbits Using a Portable Handheld System

Abstract

Purpose: : First to compare full-field ERGs from albino and pigmented rabbits; secondly to determine reliable technique and repeatability characteristics for assessing amplitude and implicit time.

Methods: : ERGs recordings were performed from both eyes on healthy 15 New Zealand and 15 Chinchila rabbits at baseline and 14 days after, using same anesthesia protocol. Fully portable ERG system (Ephiós AB, Rejmyre, Sweden) was used for data acquisition and analysis. ERG-jet and skin electrodes were used. Amplitude and implicit time were obtained by transferred data to software Mjolner v1.3:0.5. The right eye data was analyzed between races (paired t test). To assess the inter-ocular and inter-session repeatability, limits of agreement (LoA) were calculated by a percentage of the mean value i.e. % LoA = ([1.96 9 (SD test- retest)] / (mean all test and retest) x 100), where test = ERG baseline and retest = ERG after 14 days (substituted for OD and OS for inter-ocular calculations), to allow between-eye and between-session findings to be compared across techniques as described by Bland and Altman. The coefficient of variation (CoV) was also calculated.

Results: : Representative recordings between races showed larger amplitudes in albino rabbits (p<0.05), except maximal scotopic (MAX) b-wave. Interocular %LoA analysis revealed lower variability in pigmented than albino rabbits. Implicit time variability was shorter in albino animals. A normal interocular %LoA variability until 53.8% for amplitudes and 59.6% for implicit times were expected in albino rabbits. Whereas, pigmented showed 58.9% and 37.1%, respectively. Intersession %LoA amplitude and time showed higher variability in pigmented for photopic curves and lower for scotopic curves. Overall, normal intersession variability until 66.2% for amplitudes and 72% for implicit times were expected in albino rabbits. Meanwhile, pigmented showed 65.9% and 43.3%, respectively.

Conclusions: : Albino rabbits showed larger amplitudes than pigmented. Amplitude showed a normal variability until 60% (for interocular) and 66% (for intersession). The handheld full field ERG system showed representative curves and acceptable interocular and intersession variability of recordings.

Keywords: electroretinography: non-clinical