Comparison of the SRK and SRKII Formulas with Revision of Constant A in Intraocular Lens Power Calculation

ABSTRACT

The predictive accuracy of the SRK and SRKII formulas were compared in 113 pseudophakic eyes who had extracapsular cataract extraction with implantation of same type of posterior chamber IOL from Feburary 1990 to March 1991. These patients were folio we red up for at least 2 months postoperatively. Their best corrected visual acuities were above 0.5 and their astigmatisms were below 3 diopters by spectacles correction at the time of the last refraction. The results were as follows. 1. Overall, there were no significant differences in predictive accuracy between SRK and SRKII formulas. 2. The revised constant A for same type of implatnts, which constant A was 118.8. was 117.4 The SRK and SRKII formulas with revised constant A were more accurate than conventional formulas(p<0.001). 3. Our results suggested the constant A was to be revised appropriately according to the surgeon's individual regression analysis when using SRK or SRKII formulas for the calculation of intraocular lens power in Koreans.