Predictive value of regression and theoretical IOL formulas in pediatric intraocular lens implantation

Intraocular lenses (IOLs) are being implanted in children with greater frequency and in a wider age range. The accuracy of available regression and theoretical formulas in predicting correct IOL power for pediatric eyes, however, has not been reported.

We reviewed medical records of 47 consecutive pediatric IOL implantations after cataract extraction that met inclusion criteria. Age at surgery ranged from 2 months to 10 years, with measured axial lengths of the eye between 18.6 and 26.7 mm. For the purpose of this study, the 2-month postoperative refraction was considered the post-IOL refractive outcome. Using preoperative globe axial length, corneal curvature, IOL power, and the A constant for the lens provided by the manufacturer, we employed the four common IOL power formulas (one regression formula [SRK-II] and three theoretical formulas [SRK-T, Holladay, and Hoffer Q]) to predict refractive outcome.

The average difference between predicted and actual postoperative refractive error ranged from 1.2 to 1.4 diopters (D) for all formulas. Predicted postoperative refraction was less than the actual in 89 calculations and greater in 99. No significant differences in predictive accuracy were found in any of the axial length groups (group 1 P = 0.79, group 2 P = 0.42, and group 3 P = 0.86). All formulas were slightly less accurate in group 3 patients (shortest eyes). In this group, the Hoffer Q formula had the lowest error (1.4 D) and the SRK-II had the highest error (1.8 D). The difference was not statistically significant (P = .86).

In our pediatric study eyes, all four IOL power calculation formulas predicted mean refractive outcome within 1.4 D. Theoretical formulas did not outperform the regression formula.