Researchers are using the technology to start developing smart glasses that help combat myopia, one of the vision problems that affects the general population.
Nearsightedness is a common condition in which near objects appear sharp and distant ones blurry. According to a report from Australia’s Brien Holden Vision Institute, nearsightedness is increasing worldwide, especially among children. If current trends continue, half the world’s population will be myopic by 2050.
Researchers at the ZEISS Vision Science Laboratory at the University of Tübingen (Germany) and the University of Murcia (Spain) recently developed new tools to rigorously quantify and compare the light-focusing properties of specialized lenses used to slow down the vision. progression of myopia, which could lead to more effective treatments for this condition.
“Today there are different treatments to stop the progression of myopia. These include orthokeratology, atropine eye drops, multifocal soft contact lenses, and different types of ophthalmic lenses. Unfortunately, none of these methods works completely and the main proof is that the prevalence of myopia continues to increase”, Pablo Artal, professor of Optics at the University of Murcia and co-author of the study, explains to Metro.
In the new work, the scientists wanted to thoroughly characterize the currently available lenses under real viewing conditions.
“After exploring the state of the art, we did not find a method that could be used to characterize the optical properties of these spectacle lenses in real viewing conditions,” said Augusto Arias-Gallego, author of the study and member of the Laboratory of Sciences of the ZEISS Vision. “Therefore, we developed a new instrument that can measure the optical response of the lens to different angles of illumination while reproducing the pupil and refractive errors of the myopic eye.”
The new instrument uses an arm-mounted light source that rotates around the lens. After the light passes through the lens, a rotating directional mirror guides it to a spatial light modulator (SLM), made up of tiny liquid crystal cells that modify the propagated light with high spatial resolution.
The SLM is the core of the instrument, since it reproduces the refractive errors and the pupil shape of myopic eyes. This allowed the researchers to reproduce, for the first time, actual aberrations produced by different angles of illumination for different myopic eyes while testing the lenses. These aberrations were programmed as phase maps using the SLM.
In addition, programmed amounts of blur can be induced with the SLM, allowing researchers to perform a full focus test. This test captures image quality in the vicinity of a simulated retinal position, shedding light on how the lens interacts with signaled ocular elongation on the retina.
“By combining the total focusing results with the light scattering measurements, we have been able to accurately characterize various types of lenses,” says Arias.
And he concluded: next, we compared the measurements of each lens with its clinical efficacy in slowing the progression of myopia.” The results raised new questions that need to be studied further, while pointing to potential strategies that could increase the effectiveness of future designs.”
“This (new instrument) could help millions of children and is critical to understanding the mechanisms by which these lenses work.”
— Augusto Arias-Gallego, member of the ZEISS Vision Science Laboratory
Hoya MyoSmart Lens
Developed in collaboration with the Hong Kong Polytechnic University, it has multiple small blur spheres immediately outside a clear central optical zone. It has shown impressive results in slowing down axial elongation.
orthokeratology
Orthokeratology (OK), used in a new type of lens that controls the amount of extra power in the periphery by controlling the size of the optical zone, has been indicated for a temporary reduction in myopia and has also been shown to reduce progression of myopia.
Atropine
Atropine ophthalmic solution is currently the only pharmaceutical option available in the US that has been confirmed to slow the progression of myopia.
paul artal
Professor of Optics at the University of Murcia, Spain
Q: Tell us about the new instruments you developed
– We have a long history in the development of new instruments for use in ophthalmology. Specifically, we were world pioneers in the use of adaptive optics in vision, similar to that used in astronomical telescopes. In relation to the control of myopia, we can test and simulate various optical profiles to optimize their performance by stopping the progression of myopia. It will be a great new research tool in this field.
Q: How could the information obtained from this new method help design future lenses that are effective in preventing visual impairment?
– Current lens designs are based on manipulating the sharpness and contrast of images on the peripheral retina while correcting foveal vision. Although the optical characteristics of retinal images and neural responses that slow progression remain unclear, current lens designs are supported by two main hypotheses. The first hypothesis states that the growth of the eyeball slows down after imposing a peripheral myopic defocus. At the same time, competing defocus designs attempt to increase the intensity and contrast of images in front of the retina. Some of these designs incorporate microlens arrays in the peripheral side vision zone of the lenses.
Another hypothesis suggests that abnormally high contrast between adjacent cones may stimulate axial elongation. Other spectacle-based lenses have been designed to reduce contrast in the peripheral retina by incorporating micro-diffusers in its peripheral side vision zone. We have recently characterized the optical response of this type of ophthalmic lenses for the first time in an optical bench. This would help improve future designs of this type of lens.
Q: What could these future lenses look like?
– Current glasses look like normal glasses, although they have some special optical characteristics that cause blurring of retinal images. In the future, some form of optoelectronic glasses, combining optics, electronics, and computing, may do a more effective job.
Q: Could you explain how wave and light scattering is used in the new instruments?
– This type of instrument uses spatial modulators of liquid crystal light. These special devices allow light to be manipulated to produce any particular pattern. They are the central core of our technology.