Peer-reviewed veterinary case report
Measuring pupil light reflex in awake cats before and after opioids
By Magnin, Mathieu et al.·Published in Research in veterinary science·2026·Université, France·View original on PubMed →
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Original publication title: Infrared pupillometry to measure pupil light reflex in awake cats: Feasibility and evaluation pre- and post-opioid administration.
- Species:
- cat
Plain-English summary
A group of 28 cats, both healthy and sick, were tested to see how well a portable device could measure their pupil size and reaction to light before and after they received an opioid pain medication. The results showed that measuring pupil size was generally reliable, especially in sick cats, but the device struggled to accurately assess how the pupils reacted to light. Interestingly, the size of the pupils didn't change after the cats received the pain medication. While this pupillometry technique is useful for measuring pupil size, it may not be effective for evaluating pain response in cats.
People also search for: cat pupil size measurement · cat pain medication effects · why are my cat's pupils different sizes · opioid effects on cat pupils · assessing pain in cats
Abstract
Assessing pupil diameter and pupillary light reflexes (PLR) in a clinical setting can be challenging due to the pupil's sensitivity to light and the rapid nature of these reflexes. Pupillometry is a technique that is helpful in human medicine in anesthesiology and critical care medicine. However, evidence in veterinary medicine is scarce on the application of pupillometry and analgesic response. Therefore, the aim of this pilot observational study was to assess the feasibility and reliability of portable pupillometry in cats, identify individual factors influencing pupillometric parameters, and compare measurements before and after analgesic administration. Twenty-eight cats, including healthy and hospitalized sick cats, underwent pupillometry using a Neurolight® device. Pupil diameter, PLR parameters, and 4 A-VET pain score were measured before and after opioid administration. Test-retest reliability was evaluated, and the influence of factors was analyzed using multivariate models. Pupillometry was feasible in 97 % of cats, with measurements being easier in hospitalized sick cats. Good reliability was observed for pupil diameter measurements, while PLR parameters showed poor reliability. Weight was significantly associated with pupil size, potentially due to the relationship between body weight and eyeball size. No association was found between pain scores and pupil diameter, and no significant changes in pupil size were observed after opioid administration. In conclusion, portable pupillometry using the Neurolight® is feasible in cats and provides reliable pupil diameter measurements. However, the device is not suitable for objective PLR assessment in this species. Further studies are needed to better understand the factors influencing pupillometry measurements in cats.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/41270563/