Engineers at Stanford University have developed so-called autofocal lenses that overcome limitations of progressive lenses worn by people with presbyopia.
Usually experienced by people in their 40s, presbyopia causes they eye to lose the elasticity needed to focus on nearby objects. Reading glasses can rectify the problem for some, but others may need to use progressive lenses that can distort the wearer’s peripheral vision and increase the risk of falling.
“More than a billion people have presbyopia and we’ve created a pair of autofocal lenses that might one day correct their vision far more effectively than traditional glasses,” said Stanford electrical engineer Gordon Wetzstein. For now, the prototype – described in Science Advances.- looks like virtual reality goggles, but the team hopes to streamline later versions.
In a statement, Stanford said the prototype works in a similar way to the lens of the eye, with fluid-filled lenses that bulge and thin as the field of vision changes. It also includes eye-tracking sensors that triangulate where a person is looking and determine the precise distance to the object of interest. The team did not invent these lenses or eye-trackers, but they did develop the software that harnesses this eye-tracking data to keep the fluid-filled lenses in constant and perfect focus.
To validate its approach, the Stanford team tested the prototype on 56 people with presbyopia. Test subjects said the autofocus lenses performed better and faster at reading and other tasks. Wearers also tended to prefer the autofocal glasses to the experience of progressive lenses.
Wetzstein’s lab is active in vision systems for virtual and augmented reality and it was during this work that the researchers became aware of the new autofocus lenses and eye-trackers, which they combined into a potentially transformative product.
According to Stanford, the next step will be to develop autofocal glasses that are lightweight, energy efficient and stylish.
“This technology could affect billions of people’s lives in a meaningful way that most techno-gadgets never will,” Wetzstein said.
As a user of so called “progressive” eyeglasses since I was 45 years old, I can attest those are a very compromised solution, specially for people like me, that have a mix of Myopia, Astigmatism and Presbyopia, all at the same time. Many people have a difficult task adapting to them (some quit altogether). And even when the very best formulas are used, the results are mediocre at best, often having narrow field of vision at reading distances, and their peripheral vision is distorted. This development is indeed badly needed.
There are lenses and spectacles of this type already out there. I’ve seen at least one type that utilises silicone oil within a flexible lens structure, the curvature of which is dialled, up or down by means of a fluid entry valve at each frame hinge point, for attachment to an external reservoir. Another type uses rigid pairs of sliding lenses, adjusted by a finger-screwed knob at each hinge to alter focal depth. Both can extend the life of lens and frame over years of prescription changes, or permit self-assessment in certain cases, with no need of opticians.