This study aimed to evaluate the effects of tramadol on tear production, intraocular pressure (IOP) and pupil diameter (PD) in healthy dogs. Dogs were randomly assigned to receive 4mg kg-1 (n=11) and 6mg kg-1 (n=11) of tramadol hydrochloride intramuscularly. Tear production (Schirmer tear test, STT-1), IOP (applanation tonometry) and the PD (electronic pachymetry) were assessed before, 30 and 60 minutes after administration of tramadol. Data were compared by analysis of variance for repeated measures (P<0.05). Parameters evaluated before, at 30 and 60min, in dogs treated with 4 and 6mg kg-1, were respectively: (STT-1) 22.50±3.38, 21.14±3.94 and 21.09±2.99mm min-1; and 23.05±3.73,22.64±3.76 and 22.82±3.25mm min-1. (IOP) 18.14±2.68, 17.68±2.59 and 18.23±3.84mmHg; and 19.05±2.27, 18.91±2.74 and 17.64±2.34mmHg. (PD) 6.71±0.65, 7.22±1.42 and 6.90±1.39mm; and 6.25±1.08, 6.80±1.27 and 6.49±0.90mm. All parameters evaluated did not change significantly among time points and dose regimen. Based on the conditions under which the experiments were conducted, tramadol did not affect tear production, IOP and PD in dogs, and could be used as a preoperative analgesic for intraocular surgery and pain control for any cause in patients affected by uveitis, glaucoma and keratoconjunctivitis sicca
opioid; analgesic; miosis; keratoconjunctivitis sicca