Keeping an eye on pain: Characterization of pain behaviours in cats undergoing ophthalmic surgery

This study characterized the duration and frequency of ocular pain behaviours in cats before and after the administration of analgesia pre- and post- ophthalmic surgery. Thirty adult cats (13 female and 17 male neutered; 6.6 ± 4.4 years; 4.2 ± 1.0 kg), including brachycephalic (n = 24) and non-brachycephalic breeds (n = 6), were enrolled in a prospective, controlled, blinded study. Surgeries included lamellar keratectomy (n = 17), enucleation (n = 10), and eyelid or ocular annex surgeries (n = 3). Cats were video-recorded undisturbed pre- and postoperatively as well as following the administration of methadone (0.3 mg/kg IM during premedication and 0.2 mg/kg IV postoperatively). Pain assessment was performed using the UNESP-Botucatu feline pain scale - short form and the Feline Grimace Scale. A veterinary behaviourist blinded to treatments evaluated pain behaviours. Statistical analyses were performed using linear models. Brachycephalic breed and the presence of a protective collar were included as covariates. Preoperatively, the duration of 'lowered head position' (0 ± 0% and 13 ± 31%; p = 0.03), 'bilateral eye squinting and tense face' (4 ± 12% and 26 ± 38%; p < 0.001) and 'no attention to surroundings' (0.2 ± 1% and 10 ± 27%; p = 0.004) was shorter after than before methadone, respectively. Postoperatively, the duration of 'attention to surroundings (i.e., oriented head/eye/ears)' was longer after (51 ± 43%) than before methadone (9 ± 21%, p = 0.004). The duration of 'no attention to surroundings (i.e., unresponsive to the environment)' was shorter after (3 ± 9%) than before methadone (27 ± 42%, p < 0.0021). This study identified pain behaviours in cats undergoing ophthalmic surgery that are modified by analgesic treatment, contributing to pain assessment in ophthalmology.