Prediction Error After Lens Implantation in Children With Axial Length Less than 22 mm Below 2 Yrs

Abstract

Purpose: To compare the accuracy of IOL power calculation in children less than 2 years of age with axial length less than 22 mm using the SRK-T, SRK-II, and Hoffer-Q formulae. Design: Retrospective comparative study. Methods: We retrospectively analysed 68 eyes of 39 children below 2 years of age with axial length less than 22 mm who underwent cataract surgery with primary IOL implantation. We assessed the accuracy of predicted refraction using SRK-T, SRK-II and Hoffer-Q formulae in each of the eyes by calculating and comparing mean prediction error and mean absolute prediction error with each formula. Children with a minimum follow up of 6 weeks were enrolled to study the absolute prediction error. Results: Mean absolute prediction error was significantly different among the three formulae used for IOL power calculation in each eye (Friedman test, p-value=0.0009). There also existed statistically significant difference between SRK-T and SRK-II, SRK-T and Hoffer-Q, SRK-II and Hoffer-Q (Signed rank test, p-value= 0.0001). Absolute prediction error was minimum with SRK-II (1.85± 1.85) while it was maximum with Hoffer-Q (3.70± 4.01). Mean absolute prediction error with SRK-T was 2.09± 2.73. The clinical accuracy of absolute prediction error within ± 0.5D and ± 1 D was seen in 22 % and 40% of the eyes respectively with SRK-T while it was seen in 19 % and 38% of the eyes with SRK-II. Pearson correlation coefficient showed strong negative correlation between mean absolute prediction error with each of the three formulae and age at the time of surgery and also axial length. Lesser the age at surgery, more is the absolute prediction error. The shorter the axial length, more is the prediction error. There was no correlation of any of the formulae with mean keratometry reading. There existed positive correlation of SRK-II, Hoffer-Q and IOL power implanted. Higher the IOL power, more is the prediction error. Conclusion: The accuracy of SRK-T and SRK-II was comparable in calculating IOL power in children with axial length less than 22 mm and below