How fish, insects could aid presbyopic patients
Don't say the elephant nose fish never did anything for you. A new study takes inspiration from the African fish's unique retina to develop a revolutionary contact lens design for presbyopes.
The National Institutes of Health (NIH)-supported research seeks to create an electronic, autofocusing contact lens for people with presbyopia that continuously adjusts in concert with the individual's own cornea, effectively mimicking their youthful vision.
The project marries device miniaturization with a soft contact lens, using embedded sensors, cells and electrodes to analyze image sharpness, and in turn, automatically focus a liquid lens. This lens within a lens, formed from silicone oil and water, is electrically stimulated to modify surface tension and create different focal lengths. But it's all incumbent on visual information collected by a manmade sensor, typically limited in low-light conditions—until now.
Published in Proceedings of the National Academy of Sciences in March, the study finds a solution to this question of light sensitivity in nature, and specifically, the elephant nose fish. To enhance low-light conditions, the muddy-water-dwelling fish has a retina with a series of well-like structures coated in reflective sidewalls to intensify wavelengths. Similarly, researchers developed their "bioinspired photosensitivity enhancer" using the same principles: an image sensor containing thousands of tiny cups, coated in reflective aluminum, to amplify light for focusing.
The project, led by Hongrui Jiang, Ph.D., of the University of Wisconsin-Madison, also looks at insects' compound eyes, with their thousands of individual microlenses, as another possible solution for greater resolution in the contact lens.
Although the developments are promising, researchers note there are still fundamental questions about miniaturized power sources to drive the entire apparatus. The NIH notes a clinical testing prototype still may be 5-10 years off.
Promise for presbyopia
Presbyopia, a common vision condition in which changes in the crystalline lens make it difficult to focus on close objects, usually becomes noticeable in the early to mid-40s, and is a natural part of the eye's aging process. However, that doesn't make it any less troublesome. Presbyopia without optical correction results in an inability to perform once-effortless near tasks at a customary working distance without experiencing visual symptoms, notes the AOA's clinical practice guideline, Care of the Patient with Presbyopia. Reading glasses or multifocals are often prescribed to compensate, allowing wearers to see clearly and comfortably.
But there are challenges in first-time multifocal users with common complaints including difficulty navigating curbs or stairs, distorted image and night vision problems, as well as the psychological implication of using multifocals, the clinical practice guideline notes. That's why technology such as these developmental contact lenses holds promise, says Jeffrey Walline, O.D., Ph.D., AOA Contact Lens & Cornea Section chair.
"Learning from millions of years of evolution can be very valuable," Dr. Walline says. "Life has adapted to an extremely wide variety of environments. If we can use information from eons of adaptation, then use technology to mimic those adaptations to help us function more efficiently, then we truly are learning from success."
Dr. Walline adds: "If Dr. Jiang can accomplish the work he has lined up, millions of people will potentially benefit."
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