The Multiple Regression Equation Of Intraocular Pressure Measured By Three Portable Tonometers In Rabbits

Objective To investigate the accuracy of intraocular pressure (IOP) measured by schiotz tonometer, perkins tonometer and rebound tonometer in New Zealand White rabbits. Based on actual IOP using intracameral manometry and combined with eyeball physiological parameters so as to obtain the multiple regression equation of three portable tonometers, then the IOP values calibrated will provide more accurate experimental data for animal experiments.Methods1. CCT, CC, OAL, ACD, LTN and STN were respectively obtained through lenstar900and UBM in5eyes of5healthy New Zealand White rabbits.2. Under general anesthesia, the actual IOP was measured with a24G needle inserted the anterior chamber and connected to a pressure transducer, the IOP gradient was established with a24G needle inserted the vitreous cavity and connected to a balanced salt solution(BSS). Then, STV, PTV and RTV were taken simultaneously with three tonometers.3. Based on actual IOP using intracameral manometry and combined with eyeball physiological parameters, the multiple regression equation was obtained with SPSS11.5software statistical analysis for calibration.Result The mean eyeball physiological parameters:CCT=338.96±21.52μm, OAL=14.63±0.19mm, ACD=2.22±0.04mm, LTN=6.15±0.10mm, CC=51.68±1.66D, STN=339.80±47.41μm. The error range is equal to actual IOP-measurement IOP. The mean STV, PTV and RTV error range respectively was16.81±11.26mmHg,27.06±12.55mmHg and21.22±12.02mmHg, the difference was statistically significant (t=10.45, P<0.01; t=13.81, P<0.01; t=13.07, P<0.01). With elevated IOP gradient, three tonometer values had the greater error compared with actual IOP. Real IOP have a significant correlation with STV, CC and CCT, the multiple regression equation:Real IOP=141.015+1.57×STV+0.122×CCT-3.48×CC (R=0.923). Real IOP have a significant correlation with PTV and CCT, the multiple regression equation:IOP=-33.323+1.914×PTV+0.133×CCT (R=0.879). Real IOP have a significant correlation with RTV, CCT, CC, LTN and STN, the multiple regression equation:IOP=160.395+1.866×RTV+0.201×CCT+34.554×LTN2.649×CC+0.063×STN (R=0.950)Conclusion The STV, PTV and RTV have a great measuring error compared with actual IOP. In animal experiment, the IOP values measured by schiotz tonometer, perkins tonometer and rebound tonometer require regression calibration combining eyeball physiological parameters in order to reduce the error.