AIM: To study the SRK-II and SRK-T in clinic for calculating intraocular lens(IOL)in cataract patients, and to provide the basis for preoperative selection of IOL measurement formula and prediction of appropriate IOL diopter in cataract patients with different axial.

METHODS: Randomized selection of 160 cataract patients of 200 eyes with different axial from April 2013 to November 2015 admitted to the hospital were taken. There were 92 males with 120 eyes, 68 females with 80 eyes, the average age of 66.2 ± 4.36 years old. The axial length(AL)was measured by type A ultrasonography. They were divided into four groups according to AL. Patients with shorten AL were Group A, with normal AL were Group B, with lengthening AL were Group C, with extremely AL were Group D. The IOL diopter of the four groups were calculated by SRK-Ⅱ and SRK-T, and the corresponding IOL(American AMO intraocular lens)was implanted. The actual diopter at best corrected visual acuity(best corrected visual acuity, BCVA)was measured by optometry and retinoscopy at 1wk, 1, 3mo after operations. The mean absolute refractive error(MAE)was calculated.

RESULTS: The MAE of the SRK-Ⅱ and SRK-T at 1wk after operations was different with that at 1mo and at 3mo(P<0.05), that at 1mo was not significantly different with that at 3mo(P>0.05). there was no difference between SRK-Ⅱ and SRK-T in Group A(P>0.05), but there were significant differences in Group B, Group C and Group D(P<0.05). Patients of Group A more tended to become myopia at 1mo than at 1wk(P=0.035). Patients of Group B and C both got myopia shift at 1wk and 1mo after operation(P =0.84, 0.88). Patients of Group D tended to become hyperopia at 1mo than at 1wk(P=0.041).

CONCLUSION: This study shows that refraction become stable at 1mo after operations; the accuracy of the two methods are nearly same in Group A and B, while in Group C and D, SRK-Ⅱ is better than SRK-T on the comparison of MAE. SRK-T is better than SRK-Ⅱ on IOL calculation in patients with different AL.