Accuracy of intraocular lens power calculation formulae in paediatric cataract: A prospective study

Abstract

Aim: To evaluate the accuracy of four intraocular lens (IOL) prediction formulae (Hoffer Q, Holladay 1, SRK/T and Barrett Universal II) in paediatric cataract. Methods: A prospective study was conducted among all children under 15 years of age, undergoing uncomplicated cataract surgery with in-the-bag IOL implantation at a tertiary care centre. Following detailed evaluation and after obtaining informed consent, the children underwent surgery and the IOL was implanted as per a modification of Wilson and Trivedi recommendation. Prediction error (PE) and absolute prediction error (APE) were computed with each of the formulae, and it was compared across the various subgroups of age (<2 years, 2–4.9 years, 5–7.9 years, 8–10.9 years, 11–15 years) and axial length. Results: One hundred and fifty-nine eyes of 106 children were evaluated; mean age of study population was 5.26 (SD 3.48) years. Forty-nine children had unilateral cataracts, while 57 had bilateral congenital cataracts. Eighty-three (52.2%) of the operated eyes were right, and 76 (47.8%) were left. Overall value of PE was the least with Barrett II formula, which was statistically significant (P < 0.001), by non-parametric Friedman test. No significant difference was found among the formulae (P = 0.109), when APE was compared. Age group analysis shows least PE with Barrett II (P = 0.005) for <2 years age group, Barrett II and Hoffer Q (P = 0.001) in 2–4.9 years and Holladay I (P = 0.001) in 5–7.9 years groups. In terms of axial length, mean PE was least with Barrett II (P = 0.014) in axial length 18–19.9 mm, Hoffer Q (<0.001) in axial lengths 20–21.99 mm and with SRK/T (P < 0.001) in eyes from 22-23.99 mm and >24 mm. The PE of Holladay I (rho = -0.16, P value = 0.044) and Barrett II (rho = -0.16, P value = 0.046) formula was negatively correlated with age, while no correlation was found between PEs of any formula with AL. Conclusion: Barrett II and Hoffer Q formulae appear to provide the most accurate results in the younger age groups, with shorter eyes. Further prospective studies on larger samples of younger children with longer follow-ups are required, to explore the applications of Barrett II formula in the younger age group.