Abstract
Purpose :
The IOL stability in the capsular bag after the surgery largely affects the visual quality for the patients. This work explores how the size and decentration of capsulorhexis affect intraocular lens decentration and tilt by finite element modeling.
Methods :
To assess the biomechanical stability of the intraocular lens in the capsular bag, a finite element model was built of a capsular bag with capsulorhexis of different sizes and centration based on literature data (Burd 2002). The effect of capsulorhexes on IOLs with different powers was compared.
Decentration and tilt were calculated to assess the IOL mechanical stability. The long axis and short axis of the capsular bag were measured to asses its deformation. The finite element models in the study included capsular bag with capsulorhexis, IOL, zonular fibers and ciliary body. Axial movement of IOL was recorded. 4.5 mm and 5.5 mm diameter capsulorhexis were applied in the simulation, and the capsulorhexis was moved 0.5 mm or 1 mm in two perpendicular directions normal to the optical axis. The results were compared with currently published numerical and clinical studies.
Results :
Models featuring a centered 4.5 mm capsulorhexis demonstrated minimal intraocular lens (IOL) decentration (0.55 µm) and tilt (0.082°). Depending on capsulorhexis centration, IOL centration ranged from 0.51 to 2.45 µm, while tilt varied between 0.064° and 0.90°. In cases where a 5.5 mm capsulorhexis was centered, the IOL exhibited decentration of 0.43 µm and tilt of 0.084°. Conversely, a decentered capsulorhexis led to IOL decentration ranging from 1.28 to 8.30 µm, and tilt from 0.021° to 0.65°. These findings, notably smaller than clinically reported values (0.1 - 0.5 mm for IOL decentration and 0.1 - 2° for tilt), suggest a relatively stable IOL position.
Furthermore, IOLs with powers of 5 D, 20 D, and 34 D displayed limited magnitude difference on decentration, tilt, and axial movement, indicating that these differences are unlikely to result in discernible clinical consequences.
Conclusions :
The model suggests that capsulorhexis size and decentration have only a minor effect on IOL decentration or tilt that will in most cases not be noticeable to the patient. The differences caused by IOL powers are not noticeable according to the simulation.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.