Effect of body position on intraocular pressure in dogs without glaucoma

Objective-To determine the effects of body position on intraocular pressure (IOP) in dogs without glaucoma. Animals-24 healthy dogs with no evidence of glaucoma. Procedures-Dogs underwent ophthalmic examinations to ensure that no IOP-affecting ocular diseases were present. Each dog was sequentially placed in dorsal recumbency, sternal recumbency, and sitting position. For each of the 3 positions, IOP in the right eye was measured by use of an applanation tonometer immediately after positioning (0 minutes) and after 3 and 5 minutes had elapsed. The initial body position was randomly assigned; each position followed the other positions an equal number of times, and IOP measurement's were initiated immediately after moving from one body position to the next. Proparacaine hydrochloride (0.5%) was applied to the right eye immediately prior to IOP measurements. Results-Intraocular pressure was affected by body position. During the 5-minute examination, IOP decreased significantly in dogs that were dorsally recumbent or sitting but did not change significantly in dogs that were sternally recumbent. For the 3 positions, overall mean IOP differed significantly at each time point (0, 3, and 5 minutes). Mean IOP in dorsal recumbency was significantly higher than that in sternal recumbency at 0 and at 3 minutes; although the former was also higher than that in sitting position at 3 minutes, that difference was not significant. Conclusions and Clinical Relevance-Body position affects IOP in dogs. When IOP is measured in dogs, body position should be recorded and consistent among repeat evaluations.