Electroretinography in the normal koala (Phascolarctos cinereus)

ObjectiveTo perform electroretinography on normal anesthetized koalas (Phascolarctos cinereus). Animals studiedSix hospitalized koalas. ProcedureThe koalas were anesthetized using alfaxalone intramuscularly and isoflurane via face mask, then maintained on isoflurane after endotracheal intubation. After 20min of dark adaptation, electroretinograms were obtained using a handheld electroretinography (ERG) machine using a single flash protocol at three light intensities: 10mcds/m(2), 3000mcds/m(,)(2) and 10000mcds/m(2). ResultsAt 10mcds/m(,)(2) the mean b-wave amplitude and implicit time were 49.5V (SD 33.1 and 95% CI 29.9-69.0) and 87.4ms (SD +/- 6.5 and 95% CI 83.6-91.2). At 3000mcds/m(,)(2) the mean a-wave amplitude and implicit time were 70.5V (SD +/- 30.7 and 95% CI 52.3-88.7) and 20.6ms (SD +/- 3.1 and 95% CI 18.7-22.4), and the mean b-wave amplitude and implicit time were 122.8V (SD +/- 49.3 and 95% CI 93.7-151.9) and 63.1ms (SD +/- 13.2 and 95% CI 55.3-71.0). At 10000mcdsm(,)(2) the mean a-wave amplitude and implicit time were 90.8V (SD +/- 37.2 and 95% CI 68.8-112.8) and 16.1ms (SD +/- 3.1 and 95% CI 14.3-18.0), and the mean b-wave amplitude and implicit time were 148.3V (SD +/- 54.9 and 95% CI 115.9-180.8) and 67.4ms (SD +/- 8.4 and 95% CI 62.5-72.3). ConclusionElectroretinography in koalas is practical using a portable ERG system and a DTL thread electrode and allows for rapid assessment of retinal function.