Anatomical Lens Position Predictability for a Capsulotomy-Fixated Intraocular Lens in Femtosecond Laser-Assisted Cataract Surgery.

Objectives: To assess the anatomical lens position (ALP) predictability for a capsulotomy-fixated intraocular lens (IOL; FEMTIS FB-313, Teleon Surgical B.V) versus an intracapsular IOL (TECNIS 1-Piece, ZCB00V, Johnson & Johnson) implanted for age-related cataracts. Methods: Pre- and 3-month postoperative measurements from optical biometry and swept-source anterior segment OCT were analyzed. The lens position (i.e., postoperatively, ALP) was defined as the distance between the corneal endothelium and the lens equator. Multivariate linear mixed-effects models assessed the influence of preoperative biometric parameters on ALP, prediction error (PE), and absolute PE (AbsPE). Results: A total of 45 FEMTIS eyes from 32 patients and 26 TECNIS eyes from 18 patients were included. Postoperatively, the anterior chamber depth (ACD) increased by 1.10 mm in FEMTIS eyes and 1.66 mm in TECNIS eyes, while the lens position decreased by 0.59 mm and 0.34 mm, respectively. ACD and lens thickness (LT) were the strongest ALP predictors (ACD: β = +0.70, p < 0.0001; LT: β = +0.37, p < 0.0001). Separate multivariate models demonstrated strong predictive performance, with the FEMTIS achieving R2 = 0.92 and the TECNIS IOL performing even better with R2 = 0.97. In the FEMTIS group, LT influenced the PE (p = 0.006) and ACD the AbsPE (p = 0.005). In the TECNIS group, ACD influenced the PE (p < 0.0001), while AbsPE was not significantly affected by biometric parameters or formulas. Conclusions: ALP can be reliably predicted from standard biometric data, although less accurately for the FEMTIS IOL. Its anterior capsulotomy fixation likely compromises refractive accuracy with formulas inherently designed and optimized for in-the-bag IOLs, emphasizing the need for fixation-specific formula adjustments and dedicated optimization in capsulotomy-fixated IOLs.