As people age, their eyes can lose the ability to focus on nearby objects. This is particularly bad for nearsighted people, who then struggle to see near and distant objects. But glasses with concentric micro-scratches could be the awesome solution.
The lenses of our eyes actually change shape to focus on the light coming from distant objects. People whose eyes lose that ability have a condition known as presbyopia. If they have another eye condition, they can require multiple corrective lenses to have normal vision, which is where bifocals come into play. These special glasses, which really were invented by Benjamin Franklin, allow the eyes to focus on light at different distances, but wearers have to get used to constantly tilting their head to switch the lenses they're looking through.
Zeev Zalevsky, a researcher at Israel's Bar-Ilan University, may have come up with a better way. His new lenses feature 25 concentric circular structures, each made by tiny engraved rings a few hundred micrometers thick. The structures themselves are each about two millimeters wide.
Light enters each portion of the lenses in a slightly different way, as they shift the phase of the light waves and creating interference patterns. Zalevsky arranged the various rings so that they create a channel of continuous constructive interference, forming a channel of focus that runs through all 25 structures. That means that, as long as the eye is looking through any pat of that channel, it will see everything in perfect focus simultaneously.
That's arguably an improvement on how our eyes naturally work, and it definitely beats the constant tilting required by bifocals. There are some drawbacks to the lenses - they tend to reduce the contrast between images, and the eyes would loose focus if they looked away from the main channel, meaning people couldn't move their eyes freely while wearing glasses with these lenses. Zalevsky counters that both of these problems are minimal compared to the benefits gained from the improved focus, and the brain is actually able to fill in these gaps automatically if given a little time.