Flash electroretinography in standing horses using the DTL microfiber electrode.

The research aimed to evaluate a method of recording flash electroretinograms (ERGs) in sedated, upright horses using the DTL microfiber electrode. The results showed a steady increase in amplitude and implicit time during the dark adaptation process. The method used allows for detection of potential issues in the retina without general anesthesia.

Methodology

• The horses were sedated with detomidine hydrochloride injected intravenously at a dosage of 0.015 mg/kg.
• The auriculopalpebral nerve was blocked and the pupil was dilated, preparing the horses for the recordings.
• The ERGs were recorded using the DTL (active) electrode on the cornea, the reference electrode near the lateral canthus, and the ground electrode over the occipital bone.
• A white strobe light with intensities of 0.03 cd x s/m2 (scotopic) and 3 cd x s/m2 (scotopic and photopic) was used.
• Photopic and scotopic single flash and flicker responses to Ganzfeld stimulation were recorded.
• During the 20-minute dark adaptation period, the retina was stimulated every 5 minutes with single flashes at an intensity of 0.03 cd x s/m2.

Results

• The median b-wave amplitudes and implicit times were reported at various stages during the dark adaptation period. At 5 minutes, this was 43 microV and 63 ms; at 10 minutes, it was 72 microV and 89 ms; at 15 minutes, it became 147 microV and 103 ms; and at 20 minutes it reached 188 microV and 109 ms for a rod response, and 186 microV and 77 ms for a combined maximum rod-cone response.
• The measurements showed a steady increase in the amplitude and implicit time over the dark adaptation period.
• It was noted that no oscillatory potentials could be isolated during the study.

Conclusion

• The study concluded that the protocol of sedation with detomidine hydrochloride and the use of the DTL microfiber electrode facilitated the recording of high-quality ERGs.
• The presented methodology allows for the detection of possible functional problems in the retina without the associated risk of general anesthesia, making it a safer option for evaluating horses in a veterinary setting.