The effect of topical administration of atropine sulfate on the normal equine pupil: influence of age, breed and gender.

The study examines the impact of using atropine sulfate ophthalmic solution on the pupils of horses, considering variables such as age, breed, and gender. The research suggests that the Arabian breed and female gender are more susceptible to the effects of this medication.

Objective of the Study

• This research aimed to understand the reaction of horse pupils or the vertical pupil diameter (VPD) in response to a single dosage of 1% atropine sulfate ophthalmic solution. The study was particularly keen on determining the impact of age, breed, and gender on the reaction.

Methodology

• Among the participants were thirty-two horses of various ages, genders, and breeds. Each horse had no record of ophthalmic illness, and all maintained darkly pigmented irides.
• A single dose of two milligrams of atropine sulfate ophthalmic solution was topically given to the right eye of each horse, with measurements on VPD taken both pre and post-treatment for two weeks straight.
• The effect duration on the VPD was calculated for both treated and untreated eyes, with analyses further carried out on the impact of age, breed, and gender on the mean VPD, maximum VPD, and the time to reach maximum VPD.

Results

• The VPD of the treated eye was noticeably increased compared to the baseline measurements and the untreated eye across all stages of the examination.
• Horses of the Arabian breed indicated a higher mean VPD at the initial point (Day 0) as well as on several days following the treatment.
• Female horses also exhibited larger mean VPD than males on five out of a total of fifteen days.

Conclusions

• The study concluded that mydriasis (pupil dilation) after administering 1% atropine sulfate ophthalmic solution in horses can last beyond 14 days.
• It was also established that Arabian and female horses may experience higher sensitivity to effects of cholinergic blockade (prevention of neurotransmitter functioning) in the eye induced by the ophthalmic solution.