The annual Global Specialty Lens Symposium (GSLS) has established itself as the premier North American gathering to share the latest specialty contact lens information for clinicians, researchers, and industry partners alike. This year’s posters, most of which are available at www.eiseverywhere.com/ehome/gsls19/abstracts , exemplified every area of specialty contact lenses. Here I’ll discuss notable posters highlighting multifocal contact lenses for presbyopia.
Benefits of Extended Depth of Focus
Giancarlo Montani, Dip Optom, presented a poster titled “Objective and Subjective Visual Performance of a Daily Soft Contact Lens for Presbyopia.” He notes that manufacturers have traditionally produced simultaneous image contact lens designs, in which power varies with rotational symmetry around the center of the lens. Additionally, “a well-centered multifocal contact lens induces changes in the ocular higher order aberrations with a greater effect on spherical aberration, this gives an advantage to increase the depth of focus of the eye.” The author points out that “these designs are sensitive to optical centration and their decentration-induced coma.”
The poster highlights a novel soft lens design for presbyopia that increases the depth of focus of the eye without significant changes to higher-order aberrations by using a central 1.2mm “optically inactive” region. The study involved 40 subjects aged 41 to 63 years old. Visual acuity was measured at near and far for both high and low contrast for the extended depth of focus lens versus spectacle acuity.
There were differences measured between the test lens and spectacle correction, with a slight reduction of vision for distance with the test lens confirmed by measurement of high- and low-contrast visual acuity; however, results were better for intermediate and near vision. The author concluded that “the contact lens evaluated is a good option to compensate presbyopia, providing the patients good distance vision, optimal intermediate and near visual quality associated with high comfort.”
In their poster “A New Approach to Contact Lens Presbyopia Correction with fs-Laser Refractive Index Change,” Cory Leeson and colleagues point out that some of the recent advancements in intraocular lenses for presbyopia involve changing from refractive to diffractive correction. Diffractive optical options have limitations in contact lenses because multifocal lenses require smooth front and back surfaces. Additionally, the authors describe the limitations of current refractive multifocal contact lens image quality because of its dependence on pupil size and because of blink-induced decentration.
Rather than placing the diffractive optics on the lens surface, the authors propose “embedding diffractive multifocal wavefronts internally within a contact lens using ultrafast laser technology to create a gradient refractive index lens.” The novel lens design proposed is called Laser Induced Refractive Index Change (LIRIC). It is a plano hydrogel diffractive bifocal with a +2.50D add power distance-weighted diffraction efficiency (~70%/30% far/near). In 12 eyes, the visual benefit reported at near was 2.5 lines of logMAR Snellen equivalent with half a line of distance acuity lost. The authors propose this as a “next generation presbyopia-correcting multifocal.” CLS