Next generation diffractive multifocal contact lenses for presbyopia correction using LIRIC

Abstract

Purpose : Laser induced refractive index change (LIRIC) has been previously demonstrated to create high optical quality, monofocal and multifocal wavefronts in hydrogel materials. The goal of the present study was to measure visual performance of diffractive multifocal, presbyopia-correcting contact lenses (CLs) produced with LIRIC.

Methods : A high repetition-rate, femtosecond laser system was used to modify the refractive index of plano hydrogel CLs (Acofilcon B, 49% water, 170 µm central thickness). The laser was focused within the CLs and scanned throughout a 5 mm diameter optical zone while simultaneously controlling scan speed and laser power. The LIRIC process produced a diffractive structure intended to produce a multifocal wavefront with a +2.5 D add power and approximately 70/30% energy split between distance and near vision, respectively. Lens dimensions were measured before and after laser treatment with optical coherence tomography (OCT) to ensure integrity of the CLs. Visual quality was assessed in terms of through-focus high-contrast tumbling-E visual acuity (VA) in two conditions: 1) with the LIRIC diffractive multifocal (DMF) and 2) with an untreated control (CON) contact lens. Both conditions were assessed monocularly, in white light, in 12 cyclopleged eyes of 6 subjects viewing through a 4 mm diameter artificial pupil.

Results : The diffractive multifocal wavefronts were imparted into the CLs at a depth of 100 µm. Imaging the CLs with OCT revealed negligible changes in center thickness (-0.3±0.8%) and base curvature (0.5±0.6%). Subjects performed well at distance, with best-corrected distance VA for the DMF and CON lenses averaging 0.02±0.08 and -0.05±0.05 logMAR, respectively. Both lenses performed similarly for intermediate object distances between 0.5 and 1.5 D. Importantly, the DMF lens yielded significant visual benefit over the CON lens for near object distances (2.1 and 2.4 lines of visual benefit at 2.5 and 3.0 D object distances, respectively).

Conclusions : Diffractive multifocality in soft contact lenses is an effective method of increasing the eye’s depth of focus for presbyopia correction. LIRIC removes previous barriers to employing diffractive technology in soft contact lenses by preserving surface integrity and imparting the diffractive wavefront internally to the lens.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.