Initial assessment of a species-specific rebound measurement mode for non-human primates

Background Accurate measurement of intraocular pressure in non-human primates is of significant importance in veterinary clinical practice, particularly for the prevention, detection, and management of glaucoma in non-human primates. However, no veterinary tonometer is currently designed specifically for non-human primates. Objective To investigate the accuracy of the macaque-specific measurement mode of the iFalcon™ V100 rebound tonometer. Methods IOP was increased stepwise from 5 mmHg to 90 mmHg in 3–5 mmHg increments. At each target pressure, the system was stabilized for 10 s, then the iFalcon™ V100 recorded six consecutive rebound readings and their average. Each step yielded 2–3 such average values. The results were compared with a high-precision invasive pressure sensor. Linear regression and Bland-Altman analyses were performed, and the measurement range was stratified (5–30, 30–60, 60–90 mmHg) for refined assessment. Results The iFalcon™ V100 showed strong positive correlation with the invasive sensor (y = 0.99x + 0.42, R² = 0.99). The mean difference was − 0.036 mmHg (95% limits of agreement: -3.747 to 3.675 mmHg). Within the 5–30 mmHg range, agreement was excellent (mean difference: -0.063 mmHg). Acceptable agreement was maintained up to 90 mmHg. Conclusions This ex vivo study provides an initial assessment of the iFalcon™ V100 rebound tonometer in non-human primate eyes. The device showed good correlation and agreement with an invasive pressure sensor across a wide pressure range. While the sample size was limited, these preliminary findings support the potential of this species-specific measurement mode for IOP assessment in non-human primate research. Further studies with more eyes and in vivo conditions are needed to confirm its reliability and repeatability.