Interplay between multifocal optics and accommodation: implications for myopia progression

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ABSTRACT Myopia is a refractive error type of eye disorder where light is focused in front of the retina, requiring optical corrections to recover the resulting loss in visual acuity. It is a broadly significant health condition: it is estimated that by 2050 50% of the world population will be myopic. Moreover, even if myopia is compensated with spectacles, contact lenses or surgery, high myopia is linked to a higher risk of retinal detachment, glaucoma, and cataract. Strategies to halt the progression of myopia are therefore an urgent need. Myopia arises from a mismatch between ocular axial length and optical power, but the signals that prompt excessive eye growth are not well understood. Among various strategies developed for myopia control, the use of multifocal contact lenses (MCL) is gaining significant traction. A generalized working principle behind MCL design is that induced myopic defocus in the peripheral retina is protective for foveal axial growth. Initial clinical trials report encouraging reduction of myopia progression in children fitted with MCLs (generally, center-distance and high add powers) however they are still far from the desired effectiveness. Unlike MCL for presbyopia, MCLs for myopia control are prescribed on subjects that can accommodate. However, we currently do not have a good understanding of how accommodation interacts with MCLs in determining retinal image quality. This is a critical gap in knowledge as accommodation affects the very central feature of MCL design — the degree and the sign of retinal defocus. For example, depending on MCL design and individual physiological parameters, some subjects could rely on the near zones of the MCL for near vision, potentially exposing the retina to hyperopic defocus and triggering eye growth. We, a diverse team of optical engineers, physicists and neuroscientists will make use of adaptive optics simulation technologies and psychophysical paradigms to map non-invasively MCL lens patterns onto the subject’s pupil and systematically address key outstanding questions on the interplay between MCL design, accommodation, image quality and visual function with MCLs in young myopes. The group has previously developed adaptive optics technologies to test presbyopia corrections, novel methods based on wavefront sensing to quantify the accommodative response, IOL designs for presbyopia and psychophysical paradigms suited for young subjects. We are now using these capabilities, expanded to binocular simulation and testing, to understand factors underlying accommodative and binocular mechanisms of MCL-based interventions to slow down myopia. The long-term goal is to develop a mechanistic understanding that can help guide the design and personalization of MCL myopia control interventions. We plan to 1) determine the accommodative response with multifocal patterns in young myopes and emmetropes, 2) quantify the effects of various multifocal designs on foveal visual function and 3) test the role of accommodative response on the outcome success in children that have been clinically treated with multifocal contact lenses