Name

Prédiction de la position finale de l'implant après chirurgie de la cataracte à partir de la profondeur au plan équatorial du cristallin

The aim of the study is to develop and evaluate the accuracy of a new formula integrating data on the crystalline lens shape and position measured using swept-source optical coherence tomography (SS-OCT) for predicting the postoperative effective lens position (ELP).

Crystalline lens parameters were measured using the CASIA-2 device under mydriatic conditions. Axial length (AL) and white-to-white were assessed using the IOL Master 500. The final intraocular lens (IOL) position was measured by SS-OCT 1 month after surgery. The new formula was developed using multiple linear regression analysis and included depth to equatorial lens plane (DELP), lens thickness (LT) and preoperative anterior chamber depth (ACD). The coefficient of determination between the measured ELP and the ELP predicted by the new formula was compared with the SRK/T and Haigis formulas.

One hundred and fourteen eyes (80 patients) were included. The DELP was more correlated with the final IOL position than ACD (R = 0.82). The new formula yielded the best coefficient of determination (R2 = 0.75). The ELP predicted by the new formula was not significantly different from the measured ELP, whereas the ELP predicted by the SRK/T and Haigis formulas was significantly superior. The mean absolute prediction error of the ELP obtained with the new formula was also significantly smaller.

In this study, the DELP was the best predictor of the postoperative ELP followed by the preoperative ACD. The novel formula including the DELP, LT, and preoperative ACD, predicted more reliably the final IOL position compared to the SRK/T and Haigis formulas.

The CASIA-2 device is able to image in vivo the crystalline lens up to the posterior capsule during a routine eye examination. The ELD presented high individual variability. Yet, surgeons currently do not have the opportunity to adjust the overall IOL diameter to the capsular bag size prior to surgery.

The DELP seems to be a useful descriptive parameter of the anterior segment anatomy because it was not influenced by the LT whereas the ACD decreased with the thickening of the crystalline lens.

The final IOL position was deeper than the position of the equatorial lens plane because the haptics design of the Tecnis® ZCB00 is offset from the optic which suggested the development of a personalized constant for every IOL type. Moreover, the IOL diameter was larger than the capsular bag size. The capsular bag stretching and zonular fibers elongation could also explain the IOL shift. To customize the overall IOL diameter to the caspular bag size for each patient might benefit the accuracy of the new formula.

This is the first study to establish a new formula including the DELP measured by a novel commercially available SS-OCT to improve the postoperative ELP prediction accuracy in standard cataract surgery.

The new formula incorporating data on the crystalline lens shape and position measured by SS-OCT improve the preoperative ELP prediction accuracy after cataract surgery.