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

To determine the effect of clinic versus home environments on intraocular pressure (IOP) measurements in normotensive dogs.

Forty client-owned normotensive dogs.

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 = 0) and 10 min later (t = 10). Paired t-tests were performed to compare IOP in the clinic versus home and adjusted p < 0.05 followed by the Holm-Šídák correction were considered significant.

Mean IOP in the clinic (15.7 mmHg ±2.7) was significantly higher than mean IOP in the home at both t = 0 (14.2 mmHg ±2.2; p < 0.0001) and t = 10 (12.9 mmHg ±1.9; p < 0.0001). Mean IOP in the home at t = 0 (14.2 mmHg ±2.2) was significantly higher than mean IOP in the home at t = 10 (12.9 mmHg ±1.9; p = 0.0001). There was no significant effect of testing site sequence on IOP.

IOPs measured by tonometry in the clinic are elevated relative to IOPs obtained in the home, by up to 10 mmHg in one eye in this study. Changes in IOP may be rapid, as seen with the significant reduction in IOP over 10 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.