LAUSR

OBJECTIVE To compare effects of latanoprost, a topical prostaglandin analogue (PGA) commonly used to treat glaucoma and lens instability in dogs, and latanoprostene bunod, a novel PGA with a nitric oxide-donating moiety, on intraocular pressure (IOP) and pupil diameter (PD). ANIMALS STUDIED Ten ophthalmologically normal Beagle dogs. PROCEDURES Dogs were treated twice a day for 5 days in a randomly selected eye with either latanoprost or latanoprostene bunod. After a 6-week washout period, dogs were treated with the opposite drug. IOP and PD were measured at treatment times, at midday on days 1 and 5, and for 6 days post-treatment. RESULTS Both drugs significantly decreased IOP and PD. At midday on day 5 of treatment, mean IOP in eyes treated with latanoprost was 4.5 mmHg lower than the fellow eye and 3.0 mmHg lower than the same eye at baseline, while mean IOP in eyes treated with latanoprostene bunod was 5.5 mmHg lower than the fellow eye and 3.6 mmHg lower than baseline. Mean PD was 0.94 mm in eyes treated with latanoprost and 0.76 mmHg in eyes treated with latanoprostene bunod. There was no significant difference between the two drugs for either parameter at that time point (p = .372 and .619, respectively, for IOP relative to control and to baseline; p = .076 for PD) or when analyzed longitudinally. Significant diurnal variation in PD was noted and may have implications for treatment of lens' instability. CONCLUSIONS Latanoprost and latanoprostene bunod produce similar IOP reduction and miosis in normal canine eyes.