As presbyopia continues to affect an aging population, a group of electrical engineers from Stanford University have developed a new correction modality: focus-tunable eyeglasses that they call ‘autofocals’. Their design incorporates electronically controlled liquid lenses, a wide field-of-view stereo depth camera and binocular eye tracking. The camera data is used to automatically adjust the focal power of the liquid lenses based on input from the eye trackers. This approach is similar to some intraocular lens designs currently in use internationally.
The team evaluated 19 users on visual acuity, contrast sensitivity and a refocusing task. The autofocals exhibited better visual acuity when compared with monovision and progressive lenses while maintaining similar contrast sensitivity. The team also found the autofocals were faster and, compared with progressives, significantly more accurate during the refocusing task. In a separate study, 23 of 37 users ranked autofocals as the best correction for ease of refocusing.
According to the authors, if focus-tunable lenses expand to support a large enough range, both myopia and hyperopia can be corrected in addition to presbyopia—any changes to the prescription could be updated with the software, potentially eliminating the need to buy new lenses as presbyopia increases.
The authors found that users expressed a notable preference for their eye-tracked autofocals, potentially indicating that the technology to adjust the lens power may have a substantial impact on eventual user acceptance of focus-tunable eyewear. Still, the autofocal prototype was bulkier and heavier, leading to a short period of wear due to the lack of comfort. The team concluded that the autofocal prototype outperformed traditional forms of correction across several metrics, despite only being an early-stage implementation.
|Padmanaban N, Konrad R, Wetzstein G. Autofocals: evaluating gaze-contingent eyeglasses for presbyopes. Sci Adv. 2019;5(6): eaav6187.|