Variation in intraocular pressure following application of tropicamide in three different dog breeds.

Abstract

OBJECTIVE: To record intraocular pressure (IOP) of three different dog breeds following administration of one drop of 1% tropicamide. ANIMALS: Three dog breeds -- Golden Retrievers (n = 20), Siberian Huskies (n = 20) and English Cocker Spaniels (n = 36) -- were studied. PROCEDURE: IOPs were measured using a Tonopen following corneal anesthesia with a single drop of 0.5% proxymetacaine. A drop of 0.5% tropicamide was then administered bilaterally and a second IOP measurement was taken 30 min later (postdilation). The difference between the two measurements was considered as the effect of mydriasis on IOP. RESULTS: Dogs had an average IOP of 14.9 +/- 3.2 mmHg, with 95% confidence limits ranging from 8 to 22 mmHg. There were significant differences between breeds (P < 0.006) with Siberian Huskies having higher IOPs (17.2 +/- 3.7 mmHg) than the other breeds (Spaniels: 14.2 +/- 2.8 mmHg, P < 0.01; Retrievers: 14 +/- 1.9 mmHg, P < 0.001). The majority (60%) of dogs displayed 5 mmHg or less in IOP change postmydriasis. Siberian Huskies showed the highest IOP levels, and also had the greatest variability with dilation. CONCLUSIONS AND CLINICAL RELEVANCE: Interbreed variability in effect of tropicamide of canine IOP is evident.