• Autofocals: Gaze-Contingent Eyeglasses for Presbyopes

    By Lynda Seminara
    Selected By: Deepak P. Edward, MD

    Journal Highlights

    Science Advances
    2019;5(6):eaav6187

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    Presbyopia, which affects a substan­tial percentage of aging adults, still does not have an ideal solution. Each option—from spectacles to accom­modating IOLs—has drawbacks. Padmanaban et al. designed a correc­tion device for presbyopia, which they called “autofocals,” aimed at mimicking the natural accommodation response by combining eye tracker and depth sensor data to automatically drive focus-tunable lenses. Testing in two studies showed that autofocals outper­formed traditional corrective lenses on visual acuity and refocusing ability.

    The authors’ wearable prototype in­corporates three elements: 1) electroni­cally controlled liquid lenses; 2) a wide field-of-view stereo depth camera; and 3) binocular eye tracking. This autofo­cal system can automatically adjust the focal power of the liquid lenses based on input from the eye trackers. Because just 0.5 degrees of gaze direction error in each eye tracker is enough for perceivable changes in sharpness, the authors devised a custom sensor fusion algorithm that incorporates a depth camera. The depth serves as an extra stream of information to continually adjust for errors in eye tracking.

    In the first study of the experimen­tal device (19 participants), the visual acuity achieved with autofocals at all tested distances was superior to that with monovision or progressive lenses, and contrast sensitivity was similar. For refocusing, autofocals were faster and much more accurate than progressive lenses. In the second study, 23 of 37 users considered autofocals the best device for ease of refocusing.

    Overall, users preferred these eye-tracked autofocals to a previously proposed depth-tracked system, sug­gesting that the technology chosen for adjusting lens power may substantially affect user acceptance of focus-tunable eyewear. The comfort, convenience, and ease of use of autofocals warrant further exploration.

    The original article can be found here.