Analgesic effect of topical and subconjunctival morphine in dogs after phacoemulsification: A pilot study.

OBJECTIVE:To determine the efficacy of a single treatment of topical and subconjunctival 0.1% preservative-free morphine sulfate (PFMS) in providing analgesia following phacoemulsification in dogs. ANIMALS STUDIED:Ten diabetic and ten non-diabetic client-owned dogs treated with bilateral phacoemulsification. PROCEDURES:A prospective, randomized, masked, negative-controlled clinical trial was performed. All dogs received topical (0.2 mL) and subconjunctival (0.1 mL) 0.1% PFMS in one eye following phacoemulsification. The other eye received an equal volume and mode of administration of balanced salt solution (BSS). Ophthalmic examination, blinking rates, tearing, conjunctival hyperemia, aqueous flare, and central corneal esthesiometry (CCE) were evaluated in all eyes 1 day prior to surgery and at 4, 24, and 48 hours after surgery. Complete physical examination, ocular ultrasound, electroretinogram, hemogram, and serum biochemistry panel were performed in all dogs prior to phacoemulsification. All dogs received the standard of care treatment before and after surgery, including uniform anesthetic protocol. RESULTS:Baseline ophthalmic exams were unremarkable, except for the presence of cataracts, in all dogs. The mean CCE (±SD) at 4 hours post-operatively was 1.76 ± 1.27 g/mm2 and 1.85 ± 1.5 g/mm2 for the negative control and PFMS groups, respectively. There were no statistical differences in blepharospasm, conjunctival hyperemia, tearing, aqueous flare, blinking rates, CCE, or intraocular pressure (IOP) between the treatment groups for any of the time points for the non-diabetic and diabetic dogs, or for all dogs combined (P > .05). CONCLUSIONS:Topical and subconjunctival 0.1% PFMS did not affect the evaluated parameters after phacoemulsification in the study dogs at the timepoints assessed.