Comparison of the effects of topical and systemic atropine sulfate on intraocular pressure and pupil diameter in the normal canine eye.

OBJECTIVE: To compare the effects of topical 1% atropine sulfate and systemic 0.1% atropine sulfate on the intraocular pressure (IOP) and horizontal pupil diameter (HPD) in the canine eye. PROCEDURES: Four groups, each containing 10 dogs of varying age, breed, and sex were treated as follows: (i) One 30 µL drop of topical 1% atropine sulfate was applied unilaterally in each dog, (ii) A control group, one drop of 0.9% saline was used, (iii) 0.06 mg/kg atropine sulfate was given by intramuscular injection, and (iv) Control with saline injected intramuscularly. In all groups, IOP and HPD were measured every 5 min over 60 min. RESULTS: Topical atropine significantly increased IOP in the treated eye with no change in the untreated eye. A maximum increase in IOP from 17.7 ± 3.1 to 20.3 ± 3.1 mmHg (14.7% increase) was obtained 23.0 ± 14.3 min post-treatment. Maximal HPD of 12.1 ± 1.7 mm in the treated eye occurred 46.5 ± 6.3 min after treatment, with no increase in the untreated eye. Systemic atropine caused an increase in IOP in both eyes, showing a maximum at 15.5 ± 10.6 min post-treatment with an IOP of 17.3 ± 4.6 mmHg in the right eye and 17.1 ± 5.2 mmHg in the left eye (21.8% increase in the right eye and 21.6% in the left eye). Maximal HPD was noted in both eyes 30.0 ± 11.6 min after treatment. CONCLUSIONS: Atropine sulfate causes a significant increase in IOP when given both topically and by intramuscular injection. It should be used with caution, or indeed avoided entirely, in dogs with glaucoma or in those with a predisposition to the condition.

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, 20 mg/kg ketamine hydrochloride was injected intravenously; in the second, 0.5 mg/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 5 min for 35 min in the first group, and 60 min in the second and third group. RESULTS: A maximum increase in IOP was obtained 5 min after ketamine injection, with IOP of 23.2 ± 5.8 mmHg (a 45.0% increase compared to baseline) in the right eye and 22.9 ± 5.9 mmHg (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 35 min. Statistically significant increases in HPD (P < 0.05) were observed only at 5 and 25 min after ketamine injection. A significant increase in IOP was obtained 10 min after diazepam injection, showing a maximum IOP 20 ± 5.0 mmHg in the right eye (9.3% increase) and 19.9 ± 5.1 mmHg (8.7% increase) in the left eye (both significant at P < 0.05). HPD decreased during the study period, reaching the lowest level 30 min 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.