The White Coat Effect Influences Intraocular Pressure Measurements in Dogs: Comparing Tonometry Values Obtained in the Clinic Versus Home.

Abstract

OBJECTIVE: To determine the effect of clinic versus home environments on intraocular pressure (IOP) measurements in normotensive dogs. ANIMALS: Forty client-owned normotensive dogs. METHODS: In a prospective crossover study, 40 normotensive dogs were included following a complete ophthalmic examination. IOPs were measured in both eyes for each dog using a TonoVet rebound tonometer by a single observer. IOPs were measured in the clinic after the ophthalmic examination, and in the home upon initial entry by the observer (t&#x2009;=&#x2009;0) and 10&#x2009;min later (t&#x2009;=&#x2009;10). Paired t-tests were performed to compare IOP in the clinic versus home and adjusted p&#x2009;<&#x2009;0.05 followed by the Holm-&#x160;&#xed;d&#xe1;k correction were considered significant. RESULTS: Mean IOP in the clinic (15.7&#x2009;mmHg &#xb1;2.7) was significantly higher than mean IOP in the home at both t&#x2009;=&#x2009;0 (14.2&#x2009;mmHg &#xb1;2.2; p&#x2009;<&#x2009;0.0001) and t&#x2009;=&#x2009;10 (12.9&#x2009;mmHg &#xb1;1.9; p&#x2009;<&#x2009;0.0001). Mean IOP in the home at t&#x2009;=&#x2009;0 (14.2&#x2009;mmHg &#xb1;2.2) was significantly higher than mean IOP in the home at t&#x2009;=&#x2009;10 (12.9&#x2009;mmHg &#xb1;1.9; p&#x2009;=&#x2009;0.0001). There was no significant effect of testing site sequence on IOP. CONCLUSION: IOPs measured by tonometry in the clinic are elevated relative to IOPs obtained in the home, by up to 10&#x2009;mmHg in one eye in this study. Changes in IOP may be rapid, as seen with the significant reduction in IOP over 10&#x2009;min of acclimation in the home setting. Veterinarians should consider these findings when interpreting IOP values, especially in dogs that are stressed by the clinic environment.