Predicting Actual Lens Position to Generate a Novel Intraocular Lens Power Calculation Formula for Marfan Syndrome

To develop a novel intraocular lens (IOL) power calculation formula by predicting the actual lens position (ALP) in patients with Marfan syndrome who have ectopia lentis undergoing IOL implantation.

Patients with Marfan syndrome undergoing in-the-bag IOL implantation or scleral-fixated IOL (SF-IOL) implantation were prospectively recruited. ALP was calculated by adding anterior chamber depth to half of the IOL thickness, measured using the IOLMaster 700 (Carl Zeiss Meditec). A generalized linear model was developed to predict the ALP and integrated into effective lens position (ELP) predictions. A supplementary strategy was adjusting axial length (AL). The proposed formulas were evaluated by refraction prediction error (PE) and its absolute value (AE) and compared with both classic and state-of-the-art formulas.

A total of 408 patients (408 eyes) were divided into a training set and a validation set. ALP was significantly correlated with ELP, but the discrepancy increased with longer AL. A significant anterior shift of ALP was observed in the SF-IOL procedure compared to in-the-bag IOL implantation. The ALP prediction model, stratified by AL and surgical procedure, was constructed in the training set. In the validation set, the ALP-based formula demonstrated the highest proportion of AE within 1.00 diopter (D) (83.78% for AL ≤ 24 mm; 92.50% for AL > 24 mm) and significantly reduced extreme PE compared to other formulas. For SF-IOL implantation, the AL-adjusted formula was the most accurate. An online calculator was developed to facilitate its application.

The proposed formulas demonstrated superior accuracy for IOL power calculation in patients with Marfan syndrome compared to existing formulas.