Electroretinography in the normal koala (Phascolarctos cinereus)

Area of Science:

• Veterinary Ophthalmology
• Comparative Ophthalmology
• Animal Physiology

Background:

• Koalas (Phascolarctos cinereus) require specialized veterinary care.
• Assessing visual function in koalas is crucial for their health management.
• Electroretinography (ERG) is a standard diagnostic tool for evaluating retinal function.

Purpose of the Study:

• To establish electroretinography (ERG) parameters in normal, anesthetized koalas.
• To evaluate the practicality of using a portable ERG system in koalas.
• To provide a baseline for future studies on koala retinal health.

Main Methods:

• Six hospitalized koalas were anesthetized using alfaxalone and isoflurane.
• Electroretinograms were recorded using a handheld ERG device after dark adaptation.
• Single flash stimuli at three intensities (10, 3000, and 10,000 mcd s/m²) were employed.

Main Results:

• Quantitative data on a-wave and b-wave amplitudes and implicit times were obtained at different light intensities.
• Mean b-wave amplitude at 10 mcd s/m² was 49.5 μV (implicit time: 87.4 ms).
• At 10,000 mcd s/m², mean a-wave amplitude was 90.8 μV (implicit time: 16.1 ms) and mean b-wave amplitude was 148.3 μV (implicit time: 67.4 ms).

Conclusions:

• Electroretinography is a feasible and practical diagnostic technique for koalas.
• A portable ERG system with a DTL thread electrode allows for rapid assessment of koala retinal function.
• These findings establish normative ERG values for koalas, aiding in veterinary diagnostics.