Articles: PDF OnlyComparison of the SRK II™ formula and other second generation formulasSanders, Donald R. M.D., Ph.D.*, 1; Retzlaff, John M.D.2; Kraff, Manus C. M.D.3Author Information 1Department of Ophthalmology, University of Illinois at Chicago, Chicago, Illinois 2Medford, Oregon 3Chicago, Illinois *Reprint requests to Donald R. Sanders, M.D., Ph.D., 1855 West Taylor Street, Chicago, Illinois 60612. Analysis of the data performed by the Center for Clinical Research in Anterior Segment Surgery, which is funded by the American Society of Cataract and Refractive Surgery and private donations. Journal of Cataract and Refractive Surgery: March 1988 - Volume 14 - Issue 2 - p 136-141 doi: 10.1016/S0886-3350(88)80087-7 Free Metrics Abstract A simple modification of the SRK® formula was developed for use with extreme axial length cases (short and long eyes) to maximize prediction accuracy in these groups. For “average” eyes (over 75% of all cases), SRK needed no modifications to maintain maximum predictive accuracy. The new, modified SRK formula (SRK II™) was compared with current second generation formulas and the Binkhorst formula. The SRK II formula, while maintaining the simplicity and ease of the SRK, was comparable to and in some cases superior to the other formulas. Overall, 80.0% of 2,068 posterior chamber intraocular lenses from seven different manufacturers demonstrated less than one diopter of prediction error and only 0.5% had three or more diopters of error. In short eyes (<22 mm), 74.0% were corrected to within one diopter and less than 2.0% had three or more diopters of error. In long eyes (≥24.5 mm), 78.0% of cases demonstrated less than one diopter of error and less than 1.0% had three or more diopters of error. Although the SRK II formula is incorporated in most new A-scan units, the modifications are so simple that surgeons can take the standard SRK predictions and mentally calculate the modifications for extreme cases. © Williams & Wilkins 1988. All Rights Reserved.