Effect of toric IOL rotation in capsular bag on visual quality in model eyes

ObjectiveTo determine the impact of the change in the position of the toric intraocular lens (IOL) on visual quality by implanting toric IOL in the physiological capsular bag in a model eye and simulating its rotation.

MethodsUsing the optical analysis software Zemax, four Liou-Brennan model eyes with pupil diameters of 3.0 mm and 6.0 mm, with or without the angle κ, were created.A + 22.0 D ArcySof toric T4 IOL was inserted into the Liou-Brennan model eye.The toric IOL was then simulated to rotate 5°, 10°, 20°, and 30° in the physiological capsular bag (tilted 4.90° temporally and decentered 0.21 mm nasally). Changes in wavefront aberrations, residual astigmatism, and modulation transfer function (MTF) curves were examined among the different groups.

ResultsThe tilt and decentration of the toric IOL in the physiological capsular bag caused increases in both higher-order and lower-order aberrations, as well as an increase in residual astigmatism and a reduction in MTF values.Additionally, as the degree of rotation of the toric IOL increased, the aberrations and residual astigmatism increased gradually (for model eyes with 3-mm pupil diaters and no angle κ, rotating the IOL from 0° to 30° increased the residual astigmatism from 1.41 to 7.74 D). The rotation of the toric IOL primarily caused changes in lower-order aberrations (for model eyes with 3-mm pupil diaters and no angle κ, rotating the IOL from 0°to 30° increased astigmatism from 0.054 μm to 0.909 μm), with an increase in oblique trefoil aberration (for model eyes with 3-mm pupil diaters and no angle κ, rotating the IOL from 0° to 30° increased the oblique trefoil aberration difference from 0.000 μm to -1.481 μm), while the changes in coma and spherical aberrations were not significant.Furthermore, as the pupil diameter and angle κ increased, greater lower-order and higher-order aberrations were introduced, and the MTF values decreased.

Conclusions  When the toric IOL is centered, it provides good optical quality.When the toric IOL rotates in the physiological capsular bag, its ability to correct astigmatism gradually weakens and the imaging quality deteriorates.Additionally, pupil diameter and angle κ also affect the visual quality after toric IOL implantation.