Electroretinography in the normal koala (Phascolarctos cinereus)

Abstract

To perform electroretinography on normal anesthetized koalas (Phascolarctos cinereus). Six hospitalized koalas. The koalas were anesthetized using alfaxalone intramuscularly and isoflurane via face mask, then maintained on isoflurane after endotracheal intubation. After 20 min of dark adaptation, electroretinograms were obtained using a handheld electroretinography (ERG) machine using a single flash protocol at three light intensities: 10 mcd s/m(2) , 3000 mcd s/m(2) , and 10,000 mcd s/m(2) . At 10 mcd s/m(2) , the mean b-wave amplitude and implicit time were 49.5 μV (SD ± 33.1 and 95% CI 29.9-69.0) and 87.4 ms (SD ± 6.5 and 95% CI 83.6-91.2). At 3000 mcd s/m(2) , the mean a-wave amplitude and implicit time were 70.5 μV (SD ± 30.7 and 95% CI 52.3-88.7) and 20.6 ms (SD ± 3.1 and 95% CI 18.7-22.4), and the mean b-wave amplitude and implicit time were 122.8 μV (SD ± 49.3 and 95% CI 93.7-151.9) and 63.1 ms (SD ± 13.2 and 95% CI 55.3-71.0). At 10,000 mcd sm(2) , the mean a-wave amplitude and implicit time were 90.8 μV (SD ± 37.2 and 95% CI 68.8-112.8) and 16.1 ms (SD ± 3.1 and 95% CI 14.3-18.0), and the mean b-wave amplitude and implicit time were 148.3 μV (SD ± 54.9 and 95% CI 115.9-180.8) and 67.4 ms (SD ± 8.4 and 95% CI 62.5-72.3). Electroretinography in koalas is practical using a portable ERG system and a DTL thread electrode and allows for rapid assessment of retinal function.