Flash Visual Evoked Potentials in Conscious Horses: A Preliminary Study.
Authors: Palumbo Mariana Isa Poci, Resende Luiz Antonio de Lima, Olivo Giovane, de Oliveira-Filho José Paes, Borges Alexandre Secorun
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Flash Visual Evoked Potentials in Conscious Horses Establishing objective, non-invasive methods to assess visual pathway function in horses could improve early detection of neurological disease, yet flash visual evoked potentials (F-VEPs)—a standard diagnostic tool in human and small animal medicine—remain underutilised in equine practice, largely due to methodological uncertainty. Palumbo and colleagues successfully recorded F-VEPs from 20 healthy, unsedated adult horses using standard electroencephalography equipment without mydriasis or anaesthesia, generating normative reference values for the primary positive peak (P53) of 52.76±2.37 milliseconds, flanked by negative peaks at 38.14±4.62 ms and 72.35±5.33 ms, with peak-to-peak amplitudes of 11.85–22.81 microvolts. Critically, sedation with either xylazine or detomidine significantly compromised result reliability by depressing amplitudes and prolonging latencies, or eliminating responses entirely, indicating that conscious recordings provide superior diagnostic utility. These baseline values now provide a foundation for clinical application in identifying optic nerve and central visual pathway dysfunction, though practitioners should note that the technique requires patient cooperation rather than chemical restraint, and further investigation is needed to determine how common equine ophthalmological and neurological conditions alter these parameters.
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Practical Takeaways
- •Flash VEP is now a viable clinical diagnostic tool for equine neurological patients and can be performed without sedation or special equipment, making it practical for field or clinic use
- •Established normal values provide a reference standard for detecting visual pathway abnormalities in horses with suspected neurological disease
- •If VEP testing is needed diagnostically, avoid sedation as it significantly alters results and prevents reliable interpretation
Key Findings
- •Flash VEPs can be reliably recorded in nonsedated horses without mydriatic drugs or anaesthesia, with mean P53 latency of 52.76±2.37 ms
- •Normal reference values established: N38 latency 38.14±4.62 ms, N72 latency 72.35±5.33 ms, and peak-to-peak amplitudes of 11.85±6.21 µV and 22.81±11.50 µV
- •Sedation with xylazine or detomidine significantly affected F-VEP results by depressing amplitudes, increasing latencies, or obscuring responses entirely
- •Methodology enables clinical use of F-VEP as a diagnostic tool in horses with neurological disease using established normal reference values