Agreement Of Intraocular Pressure Values Measured By Rebound Tonometer And Goldmann Tonometer, Non Contact Tonometer In Patients After Vitrectomy Surgery

Purpose:The rebound tonometer is a new portable tonometer that measures intraocular pressure (IOP) with a new rebound method. The purpose of this study is to assess the accuracy and validity of the RBT IOP measurements by comparing them against other portable tonometers: GAT applanation tonometer and NCT tonometer.Methods:Fifty-two subjects (52 eyes) after pars plana vitrectomy were assessed with each of the tonometers:rebound tonometer, Goldmann applanation tonometer, non contact tonometer. They were selected from June 2009 to December 2009.Aged form 7 to 83 years (mean±SD, 50.7±19.27).These subjects were randomly divided into two groups. Patients undergoing vitrectomy with air/perfluoropropane(C3F8) group(group 1,n=35).Patients undergoing vitrectomy with solution/ silicone oil(SOL) group(group 2,n=17).。Each of the patients repeated the tonometer measurement 3 times (once every 10 min).One-way ANOVA method was used in data statistics. Regression analysis was used to evaluate the relationship between rebound tonometer and the remaining tonometers used in this study. Tonometers were also compared by plotting the difference between the methods against the mean,the 95% limits of agreement (LoA) were calculated. Data were analyzed utilizing the statistical package SPSS.Results:Group1 (Patients undergoing vitrectomy with air/C3F8 group):mean intraocular pressures(IOPs±SD) obtained using the three intruments were GAT 17.83±5.95mmHg,NCT 19.35±5.71mmHg, RBT 19.10±7.92mmHg.Approximately 65.7% of the IOP differences between RBT and GAT fell within±3 mmHg.whereas 40% of the IOP differences between RBT and NCT fell within±3 mmHg.A strong correlation was found between RBT and the remaining tonometers, showing correlation cofficients between GAT(R2=0.62,P<0.001)and NCT(R2=0.16, P<0.05).Group2(Patients undergoing vitrectomy with solution/SOL group):mean intraocular pressures(IOPs±SD) obtained using the three intruments were GAT 15.35±5.34mmHg,NCT 17.45±5.88mmHg, RBT 16.56±6.36mmHg.Approximately 70.6% of the IOP differences between RBT and GAT fell within±3 mmHg. So did NCT.A strong correlation was found between RBT and the remaining tonometers,showing correlation cofficients between GAT(R2=0.60, P<0.001)and NCT (R2=0.51,P<0.001).in Group 1,The signs of Bland-Altmann analysis indicate underestimation with respect to RBT of GAT and NCT for low IOPs and overestimation when pressures are higher. Whereas in Group 2, The slope of the plot with respect to RBT of GAT and NCT indicated this differences were nonsignificant.Conclusions:The three tonometers:rebound tonometer, Goldmann applanation tonometer, non contact tonometer behaved similarly when used to measure IOPs of patients undergoing pars plana vitrectomy.The limis of agreement with respect to RBT of GAT and NCT are relatively wide, so RBT can not be an alternative to GAT/NCT after vitrectomy.