Electroretinography in the normal koala (Phascolarctos cinereus).

Abstract

OBJECTIVE: To perform electroretinography on normal anesthetized koalas (Phascolarctos cinereus). ANIMALS STUDIED: Six hospitalized koalas. PROCEDURE: 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) . RESULTS: 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). CONCLUSION: Electroretinography in koalas is practical using a portable ERG system and a DTL thread electrode and allows for rapid assessment of retinal function.