Objective: To study the accuracy of different formulas forecasting intracellular lens (IOL) power after excimer laser keratorefractive operation.
Methods: One hundred and twenty eyes (60 cases) underwent LASIK surgery. Before and after the surgery, the IOL powers were calculated to correct the myopia to emmetropia by experiential SRK II formula, theoretical SRK/T formula and Binkhoist II formula respectively. Then we calculated the IOL power equal to original lens power by F, and analyzed the results before and after surgery by SPSS statistical software.
Results: 1. The IOL powers were not obviously different by different formulas between pre-operative and post-operative results in low myopia (P > 0.05). In middle and high myopia there were obvious differences (P < 0.01), the postoperative results were smaller than the preoperative ones. 2. The differences of equal IOL power by different formulas were highly related to the practical corrective refractive values of the surgery. Regression formula: The difference of equal IOL power = a + b x the practical corrective refractive value of the surgery. (SRK II: a = -l.23, b = 0.72; SRK/T: a = -l.03, b = 0.52; Binkhoist II: a = -1.44, b = 0.5).
Conclusion: The IOL powers forecasted by different formulas are smaller in middle and high myopia after excimer laser keratorefractive operation than that before the operation, and can be corrected by regression formula.