Purpose: To compare the accuracy of refractive outcomes in children undergoing secondary in-the-bag or cilliary sulcus IOL implantation, using aphakic refraction (AR)-based formulae and biometry-based formulae.
Methods: In this retrospective study, 39 eyes of the in-the-bag IOL group and the other 26 eyes of the sulcus-implanted IOL group. Holladay 1, Hoffer Q, SRK/T and SRK II formulae were employed depending on the biometric data, while Hug and Khan formulae were used based on preoperative aphakic refraction. The prediction error (PE) and the absolute value of predicted error (APE) were compared between the two groups and formulae.
Results: In the in-the-bag IOL group, non-significant differences of APE were found among the 6 formulae, while the Holladay 1, Hoffer Q, SRK/T and SRK II all demonstrated a significant hyperopic shift of median PE value compared to the Hug formula and Holladay 1 and SRK II also showed a significant hyperopic shift of PE compared to the Khan . Higher percentages of eyes with PE less than 1 D were found using Hoffer Q and SRK/T. In the sulcus-implanted group, the Holladay 1, Hoffer Q and SRK/T had a significantly smaller median value of APE than the Hug and Khan formulae, and the SRK II had a significantly smaller median value of APE than the Hug formula, while Holladay 1 had the lowest value of APE. Higher percentages of eyes within PE less than 1 D were found using Holladay 1, Hoffer Q and SRK/T, while the highest was SRK/T. Significantly larger hyperopic shifts of median PE value using all the 6 formulae were found in eyes with sulcus-implanted IOL than with in-the-bag implanted IOL . In in-the-bag implanted IOL group, the Hug and Khan formulae had significantly smaller APE values when compared with the sulcus-implanted IOL group.
Conclusions: whether IOL was in the bag or sulcus implantation, almost all the formulae showed hyperopic shift, SRK/T showed the best accuracy. Biometry-based formulae were superior to AR-based formulae in accuracy of IOL power calculation, especially when IOL was implanted in the sulcus. In-the-bag IOL implantation should always be with higher priorities, especially when using AR-based formulae in IOL power calculation.