Predictability of IOL Power Calculation With Different Formulas
Purpose
To evaluate the predictability of intraocular lens (IOL) power calculation with different formulas in eyes with various axial length (AL).
Methods
Retrospective and comparative study of 101 eyes who underwent cataract phacoemulsification with implantation of aspheric monofocal IOL (AcrySof IQ®). Preoperative AL and keratometric values (Ks) were measured by IOL optic Master® biometrics 500 (Carl Zeiss Meditec) device. Patients were divided into 3 groups based on AL: ≤ 22mm (Group 1), 22-25mm (Group 2), ≥ 25mm (Group 3). The power of the implanted IOL was used to calculate the predicted postoperative spherical equivalence (SE) by various formulas: SRKT, HOFFER Q and HOLLADAY II. The predictive accuracy of each formula was analyzed by comparing the difference between the actual and predicted postoperative SE. Statistical analysis: Student t test and analysis of variance ANOVA, p≤0,05
Results
The difference between the refractive error suggested by each formula and postoperative spherical equivalent was: Group 1 (n = 28) 0.62 D, 0.57 D and 0.59 D, statistical significance (p = 0.0001 in each group); Group 2 (n = 46) 0.29 (p = 0.0006), 0.24 (p = 0.004), 0.30 (p = 0.0004) and Group 3 (n = 27) 0.31 D (p = 0.002), 0.28 D (p = 0.004) and 0.30 D (p = 0.001) with SRKT Hoffer HOLLADAY Q and II, respectively.
Conclusion
Refractive error suggested by formulas studied was similar regardless of the axial length, being less the one provided by the HOFFER Q formula in the 3 study groups.