AIM: To assess the repeatability and reproducibility of Tonolab tonometer in rats with high intraocular pressure(IOP) and evaluate its ability to detect IOP changes in rats with general anaesthesia.METHODS: Left eyes of adult Fischer rats(F344) were photocoagulated by 532 nm diode laser to induce high IOP. Hypertensive eyes of 30 conscious rats were randomly chosen to measure IOP on a single occasion.Two observers independently and alternately undertook IOP measurements consecutively for three times using the same Tonolab tonometer blind to the other observer’s IOP measurements. The within subject standard deviation(Sw), coefficient of variation(CVw)(100 ×Sw/overall mean), and intraclass correlation coefficient(ICC) were calculated to evaluate intra-observer repeatability. Inter-observer difference was analysed by using 95% limits of agreement described by Bland-Altman and paired sample t- test. Also, another13 normal F344 rats were intraperitoneally administrated with ketamine/xylazine or chloral hydrate, and IOPs of both eyes were measured by a single operator once every 5min until animals came to conscious. IOPs at various time points were compared by using one-way ANOVAs.RESULTS: Mean IOP was 35.58 mm Hg(range 17.33 to65.33 mm Hg). For intraobserver repeatability, the Sw,CVw and ICC of high IOP for two observers were 5.20 mm Hg/3.41 mm Hg, 9.98% /8.08% and 0.820/0.928 respectively.The inter-observer difference was 14.76% ±19.76% of the mean IOP of two observers, with a 95% limits of agreement-23.97% to 53.50%, and the difference between mean IOP of these two observers was statistically significant(P =0.001). IOPs dropped slightly during the first 15 min post-aneathesia, with a IOP change between0.17 and 1.17 mm Hg. IOPs changed from basline of11.75 ±2.05 mm Hg(n =12) to 8.75 ±1.06 mm Hg 20 min post-anesthesia(P =0.001), and this hypotensivecondition persisted until 80 min post-anesthesia. CONCLUSION: In this sample of hypertensive rats,Tonolab measurements demonstrated high levels of intraobserver repea
