A Method for Measuring Intraocular Pressure in Wild-Type Zebrafish Using Rebound Tonometry: Characterization, Sex Differences, and Long-Term Repeatability

Intraocular pressure (IOP) monitoring is a critical aspect of diagnosis, and management of ocular diseases. Therefore, a tractable vertebrate model capable of reliable IOP characterization is highly desirable. The present study aims to perform a preliminary investigation of a handheld rebound tonometer to stably measure IOP and further characterize baseline IOP values in the zebrafish model. The IOP in both eyes (oculus dexter, OD, and oculus sinister, OS) of wild-type zebrafish was measured using the iCare PRO rebound tonometer at the same time points on testing days for 18 months. The long-term IOP values of male zebrafish (3–21 months) were range from 21.96 ± 0.99 to 23.39 ± 0.32 mm Hg (OD) and 22.10 ± 0.93 to 23.38 ± 0.26 mm Hg (OS), while insignificant difference was noted among testing days ( p > 0.05). Similarly, insignificant difference was observed in female zebrafish with IOP values range from 22.10 ± 1.12 to 23.19 ± 0.72 mm Hg (OD) and 22.30 ± 1.00 to 23.15 ± 0.36 mm Hg (OS) ( p > 0.05). A comprehensive evaluation of IOP profiles confirmed no significant differences based on gender, time point, and between eyes. These findings indicated that our iCare tonometer-based experimental methods provide high measurement and time-point consistency, confirming their long-term reproducibility and reliability in measuring IOP in the zebrafish.