Color blindness, also known as color vision deficiency, affects approximately 8 percent of males and 0.5 percent of females worldwide. The extent to which a person’s eyesight is impacted varies from reduced sensitivity to certain wavelengths of light, in conditions such as deuteranomaly (green light) and protanomaly (red light), to a complete absence of color in their vision, called monochromacy (achromatopsia).
If you are one of these people, researchers from Tel Aviv University, Israel, may be able to bring some color back into your life. Teaming ultra-thin optical devices, known as metasurfaces, with off-the-shelf contact lenses, the team have managed to lessen deuteranomaly, a form of red-green color blindness.
When there are anomalies in one of the three classes of cone cells (S, M, L) in the human eye, located at the back of the retina, problems in color vision can occur. For example, if the M-cone, which mainly absorbs green light, comes out of alignment, it may overlap more with the spectrum of light that the L-cone absorbs. This can diminish the number of hues the eye can distinguish, leading a person to experience a different view of the world.
“Problems with distinguishing red from green interrupt simple daily routines such as deciding whether a banana is ripe,” Sharon Karepov, a member of the research team from Tel Aviv University in Israel, said in a statement. “Our contact lenses use metasurfaces based on nano-metric size gold ellipses to create a customized, compact and durable way to address these deficiencies.”
One known way to mitigate the problems of color blindness is to reduce the detection of the excessively perceived color. Previously, this correction concept has been used in glasses, but Karepov and her colleagues, whose findings are published in Optics Letters, believe their contact lenses could be another way forward for helping people with color blindness.
“Glasses based on this correction concept are commercially available, however, they are significantly bulkier than contact lenses,” Karepov explained. Based on simulations of color vision deficiency, their contact lenses were found to restore color contrast and improve color perception up to a factor of 10.
However, their discovery was not made without a bump in the road, coming from the shape of the contact lens itself. The artificially fabricated metasurfaces are traditionally used on flat surfaces, so the team had to develop a technique to transfer them onto the curved lens. Whilst they managed to avoid altering the properties metasurface in the transfer, the material itself can be tweaked to achieve different effects on the light transmitted through them. Therefore, other vision disorders may also be alleviated by the researcher’s findings.
“Because the proposed optical element is ultrathin and can be embedded into any rigid contact lens, both deuteranomaly and other vision disorders such as refractive errors can be treated within a single contact lens,” Karepov said.
The lens is yet to enter any clinical trials, but in the meantime, the researchers say they will continue to improve their techniques and test for other applications.