In Vitro Optical Bench Analysis of Spherical and Aspheric Optic Design of the Same IOL Model
To analyze the optical bench quality of a spherical and an aspheric design of the same FDA-approved intraocular lens (IOL) model.
We analyzed 26 D spherical C-flex 570 C and aspheric C-flex 970 C IOLs (Rayner Intraocular Lenses Limited) using the OptiSpheric (Trioptics) optical bench. We evaluated the modulation transfer function (MTF) at 50 lp/mm and 100 lp/mm and the Strehl ratio using a 3 mm (photopic) and 4.5 mm (mesopic) aperture, respectively.
At 50 lp/mm, the MTF values were 0.783/0.784 (C-flex 570 C / C-flex 970 C) for a 3 mm aperture and 0.386/0.582 for a 4.5 mm aperture. At 100 lp/mm, the MTF values were 0.613/0.606 for a 3 mm and 0.275/0.332 for a 4.5 mm aperture. The Strehl ratio was 0.909/0.914 for a 3 mm and 0.356/0.463 for a 4.5 mm aperture.
The aspheric IOL design achieved higher MTF values at both apertures. The differences between the aspheric and spherical design were more pronounced at mesopic conditions. This suggests that patients with larger pupil sizes and/or working in mesopic conditions might benefit more from an aspheric IOL design.