The effects of ketamine hydrochloride and diazepam on the intraocular pressure and pupil diameter of the dog's eye

Objective To determine the effects of 10% ketamine hydrochloride and 0.5% diazepam on intraocular pressure (IOP) and horizontal pupil diameter (HPD) in the canine eye. Procedures Ten healthy dogs for each treatment group were used in this study. In the first group, 20mg/kg ketamine hydrochloride was injected intravenously; in the second, 0.5mg/kg diazepam was similarly injected; and in the third, a control group, 0.9% saline was used. In all groups, IOP and HPD were measured every 5min for 35min in the first group, and 60min in the second and third group. Results A maximum increase in IOP was obtained 5min after ketamine injection, with IOP of 23.2±5.8mmHg (a 45.0% increase compared to baseline) in the right eye and 22.9±5.9mmHg (a 43.5% increase) in the left eye (both significant at P<0.01). A significant IOP increase was observed throughout the research period of 35min. Statistically significant increases in HPD (P<0.05) were observed only at 5 and 25min after ketamine injection. A significant increase in IOP was obtained 10min after diazepam injection, showing a maximum IOP 20±5.0mmHg in the right eye (9.3% increase) and 19.9±5.1mmHg (8.7% increase) in the left eye (both significant at P<0.05). HPD decreased during the study period, reaching the lowest level 30min post-treatment. Conclusions This study showed a substantial increase in IOP after ketamine injection and a less substantial, but still significant increase after diazepam injection. These findings should be taken into consideration when using these drugs in dogs with fragile corneas, or in dogs predisposed or affected by glaucoma.