Clinical Impact of Measurement Timing on Intraocular Pressure in Dogs

The objective of this study is to determine whether intraocular pressure (IOP) varies with the timing of measurement after patient presentation and whether such differences significantly affect clinical interpretation.

A total of 88 eyes from 44 dogs presenting for their first ophthalmologic examination were included. All IOP measurements were performed by the same examiner at a single institution.

IOP was first measured immediately after history taking once the owner had left the examination room (IOP_0min). During the subsequent five minutes, Schirmer tear test-1 and neuro-ophthalmic examinations were performed, followed by a second IOP measurement (IOP_5min). IOP_0min, IOP_5min, and changes in IOP (ΔIOP) were analyzed according to sex, body weight, age, and visual status.

The mean IOP_0min was 16.55 ± 4.63 mmHg, and the mean IOP_5min decreased to 13.06 ± 3.44 mmHg (p < 0.001). Statistically significant IOP reduction was observed within all subgroups, including those divided according to sex, body weight, age, and visual status (all p < 0.001). Females and dogs weighing > 5 kg showed greater reductions in IOP compared to males and dogs weighing ≤ 5 kg (p < 0.05). No significant differences were observed based on age or visual status.

IOP decreases statistically significantly within minutes of patient presentation, and this reduction was observed across all subgroups. These findings highlight that the timing of IOP measurement should be standardized to ensure an accurate and reproducible assessment, ultimately allowing for precise evaluation of the patient's ocular condition.