Comparison of Intraocular Lens Power Calculation Formulae in Pediatric Eyes

Purpose: To evaluate accuracy of intraocular lens (IOL) power calculation formulae (SRK II, SRK/T, Holladay 1, Hoffer Q) in pediatric eyes. Design: Retrospective case series. Participants: One hundred thirty-five eyes of 96 children with congenital, developmental, or acquired cataracts who underwent uncomplicated cataract surgery and IOL implantation by a single surgeon over a 10-year period. Methods: Axial length (AL), keratometry (K), and manufacturer's A constant were employed in 4 common IOL power calculation formulae to predict the refractive outcome. Retinoscopy was measured at 4 to 8 weeks postoperatively and converted to spherical equivalent. For analysis, eyes were grouped by age at surgery, AL, and mean K. Main Outcome Measures: We determined the prediction error (PE) = predicted refraction - actual refraction and the absolute PE = vertical bar predicted refraction - actual refraction vertical bar. The formula that gave the best prediction (minimum PE) was determined. Results: The mean age at surgery was 6.4 years. Mean absolute PE was 1.11 for the SRK II, 0.84 for SRK/T, 0.76 for Holladay, and 0.76 for Hoffer Q formulae. There was a trend toward greater PE in eyes of younger children (<= 2 years), shorter AL (AL <= 22 mm) and steeper corneas (mean K >43.5 diopters [D]). On comparing absolute PE obtained with 4 formulae in each patient, Hoffer Q gave the minimum PE in 46% of eyes compared with 23% with SRK II, 18.5% with SRK/T, and 12.5% with Holladay 1. The SRK/T, Holladay 1, and Hoffer Q were similar in accurately predicting refractive error within +/- 0.5 D in about 43% eyes. When clinically significant deviation in PE occurred (>0.5 D), there was usually an undercorrection (72%), except for Hoffer Q, which was almost as likely to overcorrect as undercorrect (44% vs 56%). The PE was lower with office measurements when compared with anesthesia measurements, owing probably to better fixation in older children with higher ALs. Conclusion: The PE was insignificant (PE <= 0.5 D) in 43% eyes, and similar for all formulae. However, the Hoffer Q was predictable for the highest number of eyes. When the PE was >0.5 D, most formulae gave an undercorrection, except for the Hoffer Q, which the surgeon may want to consider when targeting postoperative refractions. Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article. Ophthalmology 2010; 117: 1493-1499 (C) 2010 by the American Academy of Ophthalmology.