Effect of defocus combined with rotation on the optical performance of trifocal toric IOLs

To objectively analyze the optical quality of the FineVision Toric intraocular lens (IOL) with two cylinder powers when different combinations of rotations and residual refractive errors are induced.

This study assessed the FineVision Toric IOL with two different cylinder powers: 1.5 and 3.0 diopters (D). Three different rotation positions were considered: centered, 5° and 10° rotated. An optical bench (PMTF) was used for optical analysis. The optical quality of the IOLs was calculated by the modulation transfer function (MTF) at five different focal points (0.0, 0.25, 0.50, 0.75, and 1.00 D).

The MTF averaged value of the reference situation was 38.58 and 37.74 for 1.5 and 3.0 D of cylinder, respectively. For the 1.5 D cylinder, the combination of 5° of rotation with a defocus of 0.25, 0.50, 0.75, and 1.0 D induced a decrease on the MTF of 12.39, 19.94, 23.43, 24.23 units, respectively. When induced rotation was 10°, the MTF decrease was 17.26, 23.40, 24.33, 24.48 units, respectively. For the 3.0 D cylinder, the combination of 5° with 0.25, 0.50, 0.75, and 1.0 D of defocus, induced a decrease on the MTF of 12.51, 18.97, 22.36, 22.48 units, respectively. When induced rotation was 10°, the MTF decrease was: 18.42, 21.57, 23.08, and 23.61 units, respectively.

For both FineVision Toric IOLs there is a certain optical tolerance to rotations up to 5° or residual refractive errors up to 0.25 D. Situations over these limits and their combination would affect the visual quality of patients implanted with these trifocal toric IOLs.