[The influence of two calculation methods on the outcomes of Toric intraocular lenses]

Objective: To evaluate the influence of Barrett calculator and AcrySof calculator on astigmatism correction effect. Methods: This is a randomized prospective study. A total of 64 cases (81 eyes) who planed to undergo phacoemulsification at Tianjin Medical University Eye Hospital during January 2017 and March 2018 were enrolled and divided into two groups randomly, including of the Barrett calculator group of 34 cases (41 eyes) and the AcrySof calculator group of 30 cases (40 eyes). Preoperative ocular biological parameters were measured using Lenstar LS900. The Toric intraocular lenses (IOL) plans were determined based on Barrett calculator and the AcrySof calculator for the two groups respectively. Subjective optometry was performed by phoropter and Toric IOL alignment was detected by slitlamp examination at 1 and 3 months postoperatively. Statistical analysis was taken with the data of 29 cases (35 eyes) in the Barrett calculator group and 26 cases (35 eyes) in the AcrySof calculator group, there were 20 males (25 eyes) and 35 females (45 eyes) with an average age of (72±10) years. The difference between the predicted residual astigmatism by the two calculators and the residual astigmatism obtained by postoperative optometry is the error of refractive astigmatism (ERA). The magnitude error is the algebraic difference of ERA. Vector error(VE) is a vector difference of ERA. Statistical analysis of magnitude error and VE between the two groups were taken by student's t test or rank sum test. Results: At 1 months and 3 months, the magnitude error absolute value of Barrett calculator group were (0.19±0.16)D, (0.28±0.24)D, and those of AcrySof calculator group were (0.36±0.28)D, (0.46±0.41)D, and the differences were statistically significant (t=-3.050, -2.036, both P<0.05). At 1 month postoperatively, the overall, with-the-rule astigmatism, and against-the-rule astigmatism VE of the Barrett calculator group were (0.30±0.21)D, (0.26±0.22)D, (0.37±0.26)D respectively, and those of the AcrySof calculator group were (0.47±0.33)D, (0.51±0.34)D and (0.52±0.38)D respectively, the differences between the two groups were statistically significant (t=-2.533, -2.436, -2.150, all P<0.05). At 3 months postoperatively, the overall, with-the-rule astigmatism, and against-the-rule astigmatism VE of the Barrett calculator group were (0.37±0.28)D, (0.29±0.17)D, (0.35±0.27)D respectively, and those of the AcrySof calculator group were (0.59±0.46)D, (0.54±0.37)D, (0.64±0.52)D respectively, the differences between the two groups were statistically significant (t=-2.142, -2.038, -2.481, all P<0.05).The difference of X(EV) between the Barrett calculator group and the AcrySof calculator group was statistically significant[-0.13(-0.36-0.80)D vs. 0.19(-1.01-0.71)D, Z=-2.965,P<0.01], and the difference of Y(EV) was statistically significant [-0.02(-0.51-0.64)D vs. -0.15(-0.88-1.10)D, Z=-2.076, P<0.05] at 1 months. There was no significant difference in X(EV) and Y(EV) (both P>0.05) at 3 months. Conelusion: As compared to AcrySof Toric calculator, the application of Barrett calculator in selecting Toric IOL may reduce ERA and improve Toric IOL correction outcomes. (Chin J Ophthalmol, 2019, 55:208-213).