Objective—To determine the effect of 0.005%
latanoprost solution on intraocular pressure (IOP) of
eyes of clinically normal horses and establish the frequency
of adverse effects of drug administration.
Animals—20 adult clinically normal horses.
Procedure—IOP was recorded (7, 9, and 11 AM; 3, 5,
and 7 PM) on days 1 and 2 (baseline), days 3 to 7 (treatment),
and days 8 to 9 (follow-up). Latanoprost was
administered to 1 randomly assigned eye of each
horse every 24 hours during the treatment period, following
the 7 AM IOP recording. Pupil size and the
presence or absence of conjunctival hyperemia,
epiphora, blepharospasm, blepharedema, and aqueous
flare were recorded prior to IOP measurement.
Results—IOP was reduced from baseline by a mean
value of 1.03 mm Hg (5%) in males and 3.01 mm Hg
(17%) in females during the treatment period. Miosis
developed in all treated eyes and was moderate to
marked in 77% of horses, with the peak effect
observed 4 to 8 hours after drug administration.
Conjunctival hyperemia, epiphora, blepharospasm,
and blepharedema were present in 100, 57, 42, and
12% of treated eyes, respectively, 2 to 24 hours following
drug administration. Aqueous flare was not
observed at any time point.
Conclusions and Clinical Relevance—Although IOP
was reduced with every 24-hour dosing of
latanoprost, the frequency of prostaglandin-induced
adverse events was high. Because recurrent uveitis
appears to be a risk factor for glaucoma in horses,
topical administration of latanoprost may potentiate
prostaglandin-mediated inflammatory disease in
affected horses. (Am J Vet Res 2001;62:1945–1951)
Objective—To evaluate the effect of topical administration
of 2% dorzolamide hydrochloride or 2% dorzolamide
hydrochloride-0.5% timolol maleate on intraocular
pressure (IOP) in clinically normal horses.
Animals—18 healthy adult horses without ocular
Procedure—The IOP was measured at 5 time points
(7 AM, 9 AM, 11 AM, 3 PM, 7 PM) over 11 days. On days
1 and 2, baseline values were established. On days 3
through 5, horses received 2% dorzolamide HCl
(group D, n = 9) or 2% dorzolamide HCl-0.5% timolol
maleate (group DT, 9) in 1 randomly assigned eye
every 24 hours immediately following each daily 7 AM
IOP measurement. On days 6 through 9, each drug
was given every 12 hours (7 AM and 7 PM) in the treated
eye. Measurements on days 10 and 11 assessed
return to baseline. Mixed linear regression models
compared mean IOP difference for each drug at each
Results—Mean IOP decreased significantly in all
eyes during the 2 dose/d period, compared with the
baseline, 1 dose/d, and follow-up periods.
Conclusions and Clinical Relevance—Administration
of either drug every 24 hours for short-term
treatment does not reduce IOP significantly.
Administering either drug every 12 hours induced a
significant reduction of IOP; however, controlling for
all variables, the reduction was less than 2 mm Hg.
(Am J Vet Res 2001;61:709–713)