Effect of topical pilocarpine treatment on tear production in dogs

Tear production, evaluated every 2 hours from 8 AM to 8 PM by use of the Schirmer tear test over a 3-day period, was not significantly different between left and right eyes in 12 dogs. However, a significant diurnal pattern was evident. Tear production was lowest at midday and highest in the late afternoon/early evening. After pilocarpine HCl ophthalmic solution (0.25, 1.0, or 2.0%; 1 drop) was administered topically to the left eye of each dog at 7 AM on days 4, 6, and 8, respectively, tear production was determined for both eyes every 2 hours from 8 AM to 8 PM on the day of treatment. Analysis of tear values between eyes and between each eye's treatment and pretreatment values did not reveal significant change for the treated eye, but tear production was significantly less in the untreated eye, compared with its pretreatment values and with values in the treated eye. On day 10 (48 hours after the last treatment), tear production values were not significantly different between left and right eyes, and for both eyes, were not significantly different from the mean pretreatment tear production values. Topical application of 0.25, 1.0, or 2.0% pilocarpine HCl consistently caused blepharospasm, conjunctival hyperemia, and miosis of the treated eye, without significant increase in tear production. We concluded that topical application of pilocarpine, at the concentrations used, may have little value in treating disorders involving reduced tear production.