Effect Of Withdrawing Chronic Topical Immune Modulating Treatment On Schirmer Tear Test Values In Dogs With Dry Eye Disease: Relevance To Dry Eye Studies

Purpose: To determine the effect of discontinuing chronic topical immune modulating (IM) treatment on Schirmer tear test (STT) values in dogs with dry eye disease (DED). Methods: Serial measurements of STTs from 14 dogs (16 eyes) previously diagnosed with DED were obtained before and after discontinuation of topical IM agents. Dogs with moderate to severe DED that had been well controlled with a topical IM treatment were included. After initial assessment topical IM treatment was discontinued, but topical lubricant was continued, and STT values were obtained sequentially. A mixed-effects regression model was used to evaluate the effects of age, gender, breed, clinical score, frequency of treatment, baseline STT value, and drug type on final STT values after IM withdrawal. P < 0.05 was considered statistically significant. Results: During the follow-up period after the IM treatment had been discontinued (136 +/- 29 days), 50% of the eyes (n = 8) exhibited STT values that never decreased to <10 mm/min. In the other 50% (n = 8), STT values decreased from 15.9 +/- 4.7 mm/min to 6.1 +/- 0.9 mm/min. In this group, the time it took to decrease the STT to <10 mm/min was 21.1 +/- 9.5 days. Severe clinical signs of DED and low baseline STT pre-IM treatment significantly affected STT post-IM treatment withdrawal (P < 0.05). Conclusions: The duration that a residual effect of topical IM treatment persists needs to be taken into consideration when studies are designed utilizing dogs with previous IM treatment for DED.