To perform the external validation of a model to predict postoperative axial length (AL) in children over 2 years of age who were undergoing bilateral cataract surgery with primary intraocular lens (IOL) implantation.

Validation study using a retrospective case series.

Using a population different from the one that created the model, but with the same characteristics regarding age, bilateral cataract, primary IOL implantation, and follow-up assessment, AL was estimated. The AL values estimated by the model were compared with the AL measured in the follow-ups.

In all, 55 eyes of 30 children were selected for this study; in 5 children with bilateral cataracts, only 1 eye was included. The median age at the time of surgery was 5.01 years. Follow-up AL measurements were obtained for 179 visits. The median age at the final follow-up visit was 10.15 years. The median AL measured and estimated by the model in all visits were 22.37 mm and 22.16 mm, respectively (Pearson coefficient: 0.9534; Lin correlation: 0.9258). In the Bland–Altman analysis, the 95% limit of agreement between the 2 methods (measured and estimated AL) was 0.71 to −1.19. In 3 eyes (1.68%) with AL shorter than 21.2 mm, the difference was >0.71, and in 9 eyes with AL longer than 22.5 (5.03%), it was less than −1.19. The median AL measured and estimated at the final visit were 22.69 mm and 22.43 mm, respectively.

Our previously developed prediction model for globe AL growth demonstrated good external validity by accurately predicting measured AL changes with growth in the validation cohort.