A New Extended Depth of Focus Intraocular Lens Based on Spherical Aberration

To describe a new extended depth of focus intraocular lens (IOL) design offering multifocality by the variation of spherical aberration in the central optical zone.

The new IOL (Mini WELL; SIFI, Catania, Italy) is an aspheric IOL with positive spherical aberration in the central 2-mm zone and negative spherical aberration in the pericentral 1-mm annulus, the amount of which was determined by specific optic calculation. The new IOL design was tested at the optical bench to investigate depth of focus and sensitivity to tilt, decentration, and angle Kappa. Visual acuity simulations were obtained from distance (4 m) to near (0.5 m).

Modulation transfer function (MTF) for a 3-mm pupil was 0.35 to 0.40 for distance vision and 0.25 to 0.30 for intermediate and near vision. MTF for a 4.5-mm pupil was 0.40 to 0.55 and 0.10 to 0.20, respectively. These values were not influenced by tilt up to ±2.5°, by decentration up to ±0.5 mm, or by angle Kappa up to 9°. Visual acuity simulations indicated good visual acuity up to 2.00 D of pseudoaccommodation.

The new IOL with double spherical aberration in the central 3-mm zone offered good MTF over a wide dioptric interval, suggesting good visual acuity between 4 m and 50 cm. This extended depth of focus IOL with no diffractive rings is expected to produce lower unwanted optical phenomena than current multifocal IOLs. [J Refract Surg. 2017;33(6):389-394.].