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Correcting Presbyopia with Autofocusing Liquid-Lens Eyeglasses

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Presbyopia, an age-related vision disorder, is characterized by the loss in the accommodative abilities of the human eye and manifests as an inability to focus on nearby objects. Current methods of mitigating accommodative loss include multifocal and progressive eyeglasses and contacts. These passive corrective devices partition the field of view into focal zones; hence they are unable to restore full-field accommodation. The resulting distorted images, reduced depth perception and poor visual experience cause reductions in visual acuity and significant vision impairment. In this article, we demonstrate accommodation restoration using smart, autofocusing eyeglasses based on adaptive optics, which automatically change the eyeglasses optical power to bring a line-of-sight object into clear focus.

The smart eyeglasses consist of two piezoelectric tunable liquid-filled lenses, an infrared time-of-flight distance sensor and a low-power dual-microprocessor based wireless electronic control system, housed within an ergonomic, 3D printed frame. The prototype smart eyeglass system weighs 132 g inclusive of battery. The optical resolution of our prototype system was 10.5 cycles/degree, with an undistorted angular field-of view of 93.69°. This system can restore up to 4.3D of accommodation, potentially restoring normal levels of accommodation in presbyopia subjects. The accommodation correction performance of the prototype was tested using subject-specific accommodation models developed from 5 presbyopic subjects in a separate clinical trial with average accommodation errors between 0.86D and 2.81D. The average smart-eyeglasses corrected accommodation error for the 5 subjects ranged between -0.021D to 0.016D indicating the system’s ability to perform high-accuracy real-time optical corrections. Furthermore, the system response time was 67 ms, requiring 4.86 mJ of energy per correction. At an average of one correction per second the smart eyeglasses can operate for 19 hours between charge cycles which provides users with seamless and comfortable restoration of accommodation throughout their workday.

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