A flexible contact lens that senses eye pressure and releases a drug on-demand could help treat glaucoma, the second leading global cause of blindness worldwide. The compact wireless device, which has been developed by a team of Chinese researchers and tested in pig and rabbit eyes so far, appears to detect and reduce rising eye pressure, one of the usual causes of glaucoma. Glaucoma is an umbrella term for a group of eye diseases where damage to the optic nerve, which relays visual information to the brain, causes irreversible vision loss and blindness in millions of people worldwide. Where this new research makes ground is in developing a device capable of detecting changes in eye pressure and delivering therapeutic drugs as needed. Recent efforts to develop smart contact lenses as wearable devices for treating eye conditions have either focused on sensing pressure changes in the eye or delivering a drug – but not both – and glaucoma treatment usually involves eye drops, laser therapy, or surgery to reduce eye pressure While it sounds exciting, keep in mind that as scientists continue experimenting with all sorts of nifty devices for treating eye diseases, early detection of glaucoma and timely treatment remains vital. "Once detected, therapy for glaucoma can arrest or slow its deterioration in the majority of cases," Jaimie Steinmetz, a research scientist at the Washington-based Institute for Health Metrics and Evaluation, and collaborators wrote in 2020 when analyzing the global burden of eye diseases, including glaucoma. But glaucoma is typically hard to catch because peripheral vision is the first to go, and devices used to diagnose the condition only provide snapshot measurements of intraocular pressure, which fluctuates with activity and sleep-wake cycles. "Hence the importance of improving systems of surveillance, highlighting risk among family members of cases, and effectiveness of care once treatment is initiated," Steinmetz and co-authors stress. That said, contact lenses which sit snug against the eye hold great appeal for delivering therapies for eye conditions. But incorporating electrical circuits and sensors into small, flexible, curved, and ultra-thin contact lenses presents a serious engineering challenge. For something like this to work, it needs to be sensitive enough to detect pressure changes and release precise amounts of drug on demand – all without blocking vision and irritating the eye. "It is highly challenging to install an intricate theranostic system composited by multi-modules on a contact lens," electrical engineer Cheng Yang of Sun Yat-Sen University and colleagues write in their paper. But it seems Yang and colleagues have made progress – at least in fabricating a prototype lens that has multiple sensors embedded within it to avoid possible eye irritation and a unique laser-cut snowflake design. It's designed for treating acute angle-closure glaucoma, a less common form of glaucoma that can occur with a sudden or gradual build-up of fluid pressure inside the eye. According to the researchers, the double-layered lens is coated with an anti-glaucoma drug, brimonidine, and sandwiches an ultra-thin air film in between. This air film hooks into a cantilevered electrical circuit which senses changes in intraocular pressure when the air pocket is compressed by outward pressure from the eye. If and when eye pressure reaches high-risk levels, the wireless system triggers the release of brimonidine, which flows from the underside of the lens across the cornea into the eye, pushed along by an electrical current in a process known as iontophoresis. "The double-layer lens design enabled a compact structure to accommodate multiple electronic modulus positioned in the rim region of the contact lens," meaning it shouldn't block the view of wearers, write Yang and colleagues. So far, however, the device has only been tested on pig eyeballs and live rabbits, so more research is needed before the lens can move toward clinical tests in humans. But for now, the researchers have reported that their device can detect changes in intralocular pressure, deliver anti-glaucoma drugs via iontophoresis and "rapidly reduce" eye pressure, as designed. In these experiments, rabbit eye pressure also remained low and did not rebound like it did when eye drops of brimonidine were delivered as a control treatment, so it looks somewhat promising. "This smart system provides promising methodologies that could be expanded to other ophthalmic diseases," Yang and colleagues write. What's more, the researchers say their fabrication methods are compatible with the large-scale and cost-effective manufacturing processes currently used to make computer circuit boards, so as unsightly as this device sounds, it could be made relatively easily. But of course, we'll have to keep a close eye on what any future research eventually shows. Source
