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Introduction

Recent advances in wearable electronics, combined with wireless communications, have triggered immense interest in the development of health monitoring and/or treatment technologies. The increasing demand for user-friendly health-assistive devices has led several companies to venture into developing smart technologies, one of which is the smart contact lens.

With the advent of technology advancements, contact lenses have found a wide range of applications in therapeutics, diagnostics, etc. Early research in this area employed opaque and brittle components to enable the operation of electronic devices, thus hindering the user’s line of vision and posing a potential threat of damaging the eye, apart from causing discomfort. Hence, soft lenses such as those made of poly (2-hydroxyethyl methacrylate) (pHEMA), polyvinyl alcohol (PVA), polyacrylamide (PA), polyethylene terephthalate (PET) or polydimethylsiloxane (PDMS) are commonly used in integrating sensing technology due to the user’s comfort and high oxygen permeability. This paper broadly categorizes smart contact lenses based on their applications and technologies, also presenting some recent technology advancements, with companies and institutes working in the area included.

Smart contact lens for health monitoring:

There has been a long-felt need for a non-invasive biometric sensor for painless and instant / real-time diagnosis of chronic and widely prevalent medical conditions. The smart contact lens may be used as a single-use disposable contact lens, or for use over a longer period, which would enable continuous monitoring of biomarkers for real-time monitoring of diseases. These could be fluorescent, holographic, colorimetric, or electrochemical-based technologies.

Fluorescence-based sensing technology1 involves the absorption of electromagnetic radiation of a specific wavelength by an excitable fluorophore and subsequent emission of photons with longer wavelength. Early smart contact lenses based on fluorescence-based sensing technologies involved the development of a biosensor for glucose detection through immersion in tear fluid, and using tetramethylrhodamine isothicyanate concanvalin A (TRITC-Con A) and fluorescein isothiocyanate dextran (FITC-dextran) encapsulated within hydrogel spheres that were embedded and immobilized in polymerized Nelfilcon A (PVA-based) within a contact lens mold. As glucose diffused into the spheres, the FITC-dextran molecules shifted away from TRITC-Conv A, thus resulting in decreased Forster Resonance Energy Transfer (FRET) and increased fluorescence intensity. This biosensor could track the concentration of blood glucose of patients over three hours. However, this technique seemed to have a lag time of a few minutes between the blood glucose of the patients and the result from the sensor.

Holographic sensing technology2 has found application in the detection of health conditions. Holographic elements in contact lenses are commonly used to focus incoming light. These elements are embedded in contact lenses as a means to detect various chemicals in the eye. When the holographic elements come into contact with a particular chemical, it causes the contact lens to change color. The holographic sensing technology was envisioned to measure glucose in tears for people with diabetes. However, the major shortcoming of this technology is the inability to accurately quantify the measured chemical.

Google had been working on a contact lens that could help people with diabetes by making it continually check their glucose levels3,4,5. The idea was originally funded by the National Science Foundation and was first brought to Microsoft. In 2014, Google announced a partnership with Novartis’ Alcon unit to develop the glucose-sensing smart contact lens. The company Verily, an Alphabet subsidiary, which was part of Google till 2015, was the most aggressive in bringing electronics to contact lenses for detecting blood sugar in tears; but in 2018, announced that it had discontinued the project because of the lack of correlation between tear glucose and blood glucose. Google holds patents (for e.g., US9320460, US9289123) for technologies involving use of contact lenses with sensors that sense an analyte such as glucose, alcohol, histamine, urea, lactate, cholesterol, or electrolyte ions such as sodium, potassium, calcium and magnesium in the tear fluid; and contact lenses for measuring an intraocular pressure.

Recent research has led to the development of flexible micro-LED arrays for use in wearable light sources and high tech surgical gloves. The small size, low current and low energy consumption of LEDs have led to their use in various medical applications.

A Korean research team at Ulsan National Institute of Science and Technology (UNIST) has developed smart contact lenses that are integrated with glucose sensors, wireless power transfer circuits and LEDs6, 7, 8, 9. Glucose levels present in the tears of the user are monitored real-time and the results are instantly provided via an embedded LED display. Professor Jang-Ung Park and Professor Franklin Bien, in collaboration with Professor Jung Heon Lee of Sungkyunkwan University, jointly conducted a research on the glucose level-monitoring contact lens. These smart contact lenses use electrodes made up of highly stretchable and transparent materials10. The glucose sensor present in the contact lens sends electrical signals to an LED. With this sensor, patients can transmit their health information real-time with the help of an embedded wireless antenna in the lens. Electric power activates the LED pixel. In cases where the glucose concentration in tear fluid is above the threshold, the LED pixel turns off. Additionally, it offers significant potential for expanded applicability in other areas, such as smart devices for drug delivery and augmented reality.

soft-contact-lens

A soft contact lens that will allow diabetics to monitor glucose levels in their tears(© UNIST / SWNS.com) (Source)

smart-contact-lens,-capable-of-monitoring-glucose-levels-in-tears

The new smart contact lens, capable of monitoring glucose levels in tears. (Credit: UNIST) (Source)

Sensimed, a Swiss MedTech company established in Lausanne after its spin-off from EPFL in 2003, developed SENSIMED Triggerfish®, a continuous ocular monitoring system that provides insights into the ocular volume changes throughout the day and night11, 12. The CE-marked and FDA-approved13 device includes a smart contact lens that tracks glaucoma progression by capturing spontaneous changes in the eye, providing physicians with valuable information that can help guide glaucoma treatment. Sensimed also holds patents (for e.g, US9271677) for measuring and monitoring intraocular pressure.

Sensimed has also announced the registration of the SENSIMED Triggerfish® sensor and monitoring system as a medical device in Japan. Necessary approvals to market the product in Japan have also been obtained. SEED Co Ltd, which made investments in the early stage of Sensimed, acquired a majority stake in it in November 201914.

Researchers at UNIST and Kyungpook National University School of Medicine have collaborated to develop transparent and stretchable multifunctional sensors on wearable graphene-based soft contact lenses for wireless detection of glucose and intraocular pressure with high sensitivity15. Multiplexing various sensing elements, the contact lens sensors enable wireless, continuous and non-invasive monitoring of physiological conditions as well as the detection of biomarkers associated with ocular and other diseases.

IMEC, a research and innovation hub in nanoelectronics and digital technologies, the Ghent University (UGent), and contact lens manufacturer SEED Co. Ltd. have developed a hydrogel-based contact lens with an integrated LED light, including an ultra-thin silicon microchip, radio‐frequency (RF) antenna for wireless energy transfer, and stretchable thin‐film interconnections10. These LED-light-integrated contact lenses have been developed for diagnosing and treating ocular diseases.

Start-ups have also entered the foray of smart contact lens. In November 2018, VSPARTICLE, a Dutch a spinoff company from Delft University of Technology, professed to develop a low-cost technology for printing sensors that enables smart contact lenses to perform various applications such as glucose sensing, bio-marker sensing, etc16, 17. Microoptx Inc. has developed contact lenses that can monitor the aqueous humor to determine glucose concentration as a function of polarimetry and/or fluorescence sensed by the contact lens. The present contact lenses can also be used to treat conditions such as glaucoma and dry eye10. It has filed patent applications (for e.g., US20190175083, US20180333085A1) for an implantable ocular glucose sensor device, wherein the sensor measures a concentration of glucose in the aqueous humor of the eye and wirelessly communicates measured glucose concentrations of the aqueous humor to an external device.

Research institutes/ academic institutes which have been researching in this area include POSTECH, Korea Advanced Institute of Science & Technology, University of Wisconsin, and University of Washington. Pohang University of Science and Technology (POSTECH) 18, 19, 20, 21, an independent research university based in Korea, claimed recently that its researchers have developed a smart light-emitting diode (LED) contact lens. The research team led by Prof. Sei-Kwang Hahn has developed smart photonic contact lens and wearable medical devices using light that can diagnose diabetics and treat diabetic retinopathy. Integrated with a micro-LED and photodetector, the smart contact lens can measure glucose concentration in the conjunctival blood vessels by analysing the Near-infrared (NIR) light. The device is said to work by analyzing the glucose concentration in tears via NIR light to deliver drugs for treating retinopathy. POSTECH, in collaboration with Korea Advanced Institute of Science & Technology, 22 has also filed a patent application (KR20160127322A) for a smart contact lens that includes a sensor capable of non-invasively sensing eye disease in real time, a drug delivery site, and smart glasses for controlling the smart contact lens. Reportedly, the commercialization of these smart contact lenses is being planned in collaboration with Stanford Medical10. Preliminary clinical tests are expected to be carried out in the first half of 2020. It has been reported that the smart contact lenses have resulted in low irritation in rabbits, and have been able to reliably detect glucose levels in tears, and could controllably release genistein, a compound that may help treat diabetic retinopathy23.

The University of Wisconsin has developed a lens that uses light sensors and tiny power sources to autofocus, just as a camera would, on whatever the wearer is looking at.24 New studies include testing lenses that can track the progress of glaucoma with tiny sensors.

Measurement-of-glucose-levels-in-eye-fluids

Fig. 3. Measurement of glucose levels in eye fluids (Source)

The University of Washington holds a patent (US8608310) for a wireless-powered contact lens with a glucose sensor. The contact lens includes an electrochemical sensor configured to measure the level of glucose in the tear fluid of the user wearing the contact lens. The electrochemical sensor is powered by radiation off-lens, through an RF antenna or a photovoltaic device mounted on the periphery of the contact lens. The power provided to the contact lens also enables transmission of data from the electrochemical sensor, for example, by backscatter communications or optically by an LED mounted to the lens.

Herapeutic Contact Lenses:

A contact lens with drug-eluting technology is one of the promising platforms for  controlled ocular drug delivery, due to its advantages such as extended wear and good bioavailability (more than 50%).25 Drug-eluting contact lenses have been developed to address challenges such as low bioavailability and limited exposure time to pharmacological interventions. However, these drug-eluting lenses lack the accuracy in the dosage of the drug released as well as controlled release of the drug. In light of this, there is a need for a smart contact lens that can provide more control on the rate of drug delivery and the amount of the drug being delivered, based on real-time monitoring.26

concept-of-using-nanoparticles-in-contact-lenses

Fig. 4. Schematic illustrating the concept of using nanoparticles in contact lenses for extended drug delivery (Source)

Therapeutic lenses are primarily used to provide relief from ocular pain, promote corneal healing, offer mechanical protection and support, maintain corneal epithelial hydration and deliver drugs.27 The problems associated with topical ocular administration of drugs have prompted researchers to probe alternate approaches such as mucoadhesives, viscous polymer vehicles, nanoparticles, in situ gel forming systems and iontophoresis. For instance, incorporation of novel polymeric vehicles with multifaceted features such as altered transparency and oxygen permeability help overcome these limitations, thus making it possible to deliver the drugs in a comfortable and extended manner. Encapsulation efficiency and prolonged drug release can be achieved by using polymers that have diverse physicochemical properties for nanoparticles or implants, depending on the requirement.

schematic-of-drug-delivery-routes

Fig. 5. The schematic of drug delivery routes by contact lens (Source)

Nanoparticles can be dispersed into contact lenses without impacting vision, due to their small sizes, thus eliminating scattering of visible light. The nanoparticles could be designed to have a high affinity for the drug by tailoring the hydrophobic or the ionic interactions of the drug with the particle matrix.28 Applications of these contact lenses include treatment of glaucoma, bacterial conjunctivitis, allergic rhinitis etc.

Huawei Biomed has filed a patent application (KR20180038359A) for a wireless-powered smart contact lens for diagnosing and treating diseases using a micro LED. The smart contact lens may include a photodetector with a micro LED illuminate light on disease markers, and photodetectors detect light reflected and analyze them to diagnose the disease. The drug reservoir is connected to the photodetector so that the drug reservoir can be opened upon diagnosis of the disease. Specifically, the drug release can be controlled from a drug delivery device installed in the lens through various signals according to external light wavelength through a photodetector.

OneFocus Vision Inc holds a patent (US10444543) for an accommodating contact lens comprising a control device having eyelid engagement structures that are configured to move with the eyelid relative to the fluidic accommodating contact lens. These contact lenses have the ability to auto-adjust the focus in response to the squint of the eye, thus allowing the user to control focus, independent of the direction of the gaze and head angle. As the control device is integrated with the contact lens, it enables the user to control the eyelid engagement structures for accommodation and/or therapeutic agent delivery.

In 2018, Theraoptix, a startup of Harvard Medical School, received the MIT Sloan Healthcare Innovation Prize for its innovative contact lens that enables sustained and controlled delivery of eye medicament.29, 30, 10 For its novel invention, Theraoptix took home the annual competition’s $25,000 grand prize, sponsored by health services firm Optum. The award-winning drug-delivering contact lens is made of FDA-approved materials. The lens is fitted between drug-filled polymer contact lens films, which are tiny circular strips that do not interfere with the user’s vision. The sandwich structure allows the drugs to trickle from the film into the eye. The lenses can be worn all day for up to two weeks to treat eye diseases such as glaucoma or to aid in healing after surgery. Theraoptix’s aim is primarily to improve patient compliance. Reportedly, six months into therapy, patients can stop taking medications.

Researchers of the Harvard Medical School have created contact lenses that allow medication to slowly release into the eye over the course of days or weeks.31 The contact lenses are crafted from materials approved by the Food and Drug Administration. They slowly release medication that is stored in the contact lenses’ materials. There is a small drug-filled polymer film that forms a strip around the lens itself but never interferes with the wearer’s vision.

Researchers at Tohoku University have developed a new type of smart contact lenses that can prevent dry eyes through a self-moisturizing system that maintains a layer of fluid between the contact lens and the eye, using an electro osmotic flow mechanism that causes the liquid to flow when a voltage is applied across a hydrogel, which is a charged surface.32 The contact lenses are wirelessly powered using magnesium-oxygen batteries and enzymatic fructose-oxygen fuel cells, which can be mounted directly on the charged contact lenses. However, further research is needed to develop improved self-moisturizing contact lenses that are tougher and can be operated at smaller currents.

University of Florida Research Foundation Inc. holds a patent (US8404265B2) for contact lenses for extended release of bioactive agents containing diffusion attenuators. The diffusion attenuator can be solid particles or phase-separated liquid aggregates within the continuous phase of the hydrophilic or silicone-hydrogel contact lens, where the diffusion attenuators promote a tortuous path for the bioactive agent to diffuse from the contact lens. The diffusion attenuator, such as Vitamin E, can be incorporated while forming the contact lens through polymerization of a monomer mixture. For liquid diffusion attenuators, the liquid can be co-absorbed with a solvent into the lens followed by removal of the solvent, where the bioactive agent can be co-absorbed.

University of California, apart from contact lenses for ocular drug delivery, has developed a prophylactic bandage contact lens (US2019101669) that prevents as well as treats microbial infections by dispensing antimicrobial medication at controlled rates. The bandage comprising nanostructures provides a continuous treatment over ten days and shields the eye from the environment, significantly diminishing the risk of infection while allowing damaged tissues to heal.

Augmented Reality (AR) contact lens

Augmented reality, which enables observing the real world supplemented with computer generated content, is gaining popularity in many applications. Smart contact lens could provide the ultimate augmented reality (AR) experience. They can enable users to access smart menus in their peripheral vision, by selecting a feature by simply focusing on it. The lenses could be put to an almost infinite number of uses, such as checking user’s heart-rate, providing directions, alerting users of local accidents or highlighting areas of high car or foot traffic, providing weather updates, recommending a restaurant, or reading the user’s latest instant message.

Samsung’s-multi-layered-smart-contact-lens

Fig. 7. Samsung’s multi-layered smart contact lens (Source)

Samsung Electronics Co Ltd received a patent (US10359648) for smart contact lenses with an in-built camera.33 According to Samsung Mobile’s report, Samsung started developing smart contact lenses as a means to create a better augmented reality experience than the Google glasses, which were pulled off the shelves in early 2015 due to poor image quality. The smart contact lens includes a first contact lens, a display unit in its center region, a peripheral device around the display unit, which is also connected to the same, and a passivation layer covering the display unit and the peripheral device.

Samsung also holds a patent for a utility model (CN202904132U) for contact lenses, comprising a left eye lens and a right eye lens, respectively being a red lens, and a blue or a green lens. The contact lenses are convenient to be worn, and users can easily, comfortably and reliably watch pictures displayed by 3D display equipment; by which the fatigue degree of the user watching 3D video is reduced, visual enjoyment of the user is guaranteed, life quality of the user can be improved, market application prospect of the lenses is enlarged, and the contact lenses have important production and practical significance.

The technologies developed by EP Global Communications, Inc (EPGL) in this domain revolve around manufacturing and integration of electronics into modern silicone hydrogel lenses.34 Their technology allows integration of flexible electronics into the contact lens during the manufacturing process, providing solutions in the areas of autofocus and optics for augmented reality contact lenses. EPGL anticipates that its augmented lenses will communicate with smart phone applications for display. EPGL and InWith Corp. announced that they would partner to build the “InLens 1.0” brand of electronic-augmented mobile contact lenses.10 The “InLens” line is planned to include augmented reality, autofocus and more electronic contact lens applications tied to mobile phone applications. In 2016, EPGL received a US Patent on the “Elastic Circuit”, which is an essential element for molding and mass production of soft electronic contact lenses. Electronically enhanced contact lenses are the ultimate platform for augmented vision ($150 billion estimated market), advanced forms of vision correction, diagnostics and drug delivery. “InLenses” will be built to be compatible with both Apple iOS and Google Android Operating systems. The mobile network will open the door to perhaps hundreds of vision-based display applications in future. EPGL has multiple ophthalmic patents pending in this field.35

Raayonnova LLC, a company with research activity in the area of augmented reality, virtual reality and wearables, has filed patent applications (for e.g., US20160299354A1, US20170023793A1, US10353463B2) for smart contact lenses integrated with electronic, electro-optical or optical components. Its research includes a smart contact lens system integrated with a number of electronic, electro-optical or optical components on the contact lens substrate. The system, inter alia, is arranged to identify and track changes in pupillary response due to mental task engagement, also known as task-evoked pupillary response. To this end, the proposed system tracks a variety of conditions affecting reflexes such as pupillary reflex or accommodation reflex, in order to compute the extent of pupil dilation attributable to the mental task engagement. This smart contact lens system reportedly minimizes pupillary reflex caused by light, by controlling the amount of light entering the eye. When pupillary reflex is non-existent, computing a task-evoked pupillary response becomes a much easier task. The company has also worked on smart contact lenses with an embedded display and a processor. The embedded display may form a part of the contact lens substrate. The processor is configured to shift a part of an image to a central position of the embedded display to bring it into focus.

International Business Machines (IBM) Corporation has filed a patent application (US20190227348) that deals with a computer program and a system for use with a smart contact lens for data transfer using Li-Fi (light-fidelity) communication. The Li-Fi technology operates under the principle that light can be used to carry signals as an alternative to traditional radio frequencies. The smart contact lens comprises a light-transmitting device adapted to send light signals, a data-receiving device, and a microcontroller adapted to transmit the data packets via Li-Fi communications between the two.

The Care Harmony Group’s Beneficial Vision smart contact lenses have the ability to deliver monochromatic text and video images.10 These lenses comprise a ring of rechargeable batteries and lasers, and use wave-guide technology to project an image into the central area of the contact lens. The contact lenses are combined with wireless ear buds that deliver audio and can also track the user’s head, and then relay the information to the contact lenses to ensure that the projected image is a stable overlay on the real world when there is head movement. The potential applications of these contact lenses include education, personal security, law enforcement, medical industry, aerospace industr, and entertainment. However, although only a prototype has been displayed to the public, pre-orders are currently possible.

Silicon Valley startup Mojo Vision, founded by veterans from Apple, Google, Microsoft and Amazon, is working on an invisible computing-augmented reality technology that would eliminate bulky headsets and allow users to enjoy AR via contact lenses. Mojo Vision has put 14K pixels-per-inch microdisplays, wireless radios, image sensors, and motion sensors into contact lenses that fit comfortably in the eyes.36, 37, 38

Augmented-reality-contact-lens

Fig. 8. Augmented reality contact lens (Source)

Mojo lens, considered to be a truly super-smart contact lens, uses microelectronics and a tiny display to share critical information, with the display being the center piece of the Mojo lens. It is placed directly in front of the pupil, so that it projects and focuses light toward a specific area of the retina at the back of the eye. If a person already has low vision, the lens helps the user, especially to see in the dark. Applications range from helping out drivers on the road to assisting surgeons in the operating room. The first generation of Mojo Lenses is being powered wirelessly, though future generations will have bio-safe batteries integrated into the lens so that it will enable all-day wear. A small external pack, besides providing power, handles sensor data and sends information to the display.

Mojo Vision has attracted $108 million in venture capital investments from Google’s Gradient Ventures, Stanford’s StartX fund, Khosla Ventures, HP Tech Ventures and LG Electronics, New Enterprise Associates (NEA), Shanda Group, Advantech, Motorola Solutions, Liberty Global, Fusion Fund and others. The company is led by a team of Silicon Valley veterans from various companies, including Apple, Amazon, Google, HP, Microsoft, Motorola, Infinera, Agilent and Marvell, among others; as well as medical device and optometry experts from companies such as CooperVision, Abbott, Johnson & Johnson, Medtronic, Philips Healthcare and Zeiss Ophthalmology.39, 10

Mojo Vision reportedly plans to pursue enterprise applications where hands-free access to real-time information would improve productivity. The “Mojo Lens” will be controlled by eye movements, with a user looking to the corner of their eyes to activate icons such as weather app or music player. The person can then fixedly stare at an arrow next to the icons to select them. The screen is turned off by looking away or blinking. The company is working with the FDA in the US to get the approval for these smart contact lenses.40

A team of researchers from Innovega Inc – Dr. Joe Barr, Dr. Jerry Legerton and Ron Walker received awards in the area of contact lenses at the Global Specialty Lens Symposium, for the development of lightweight, wearable display technology that has a panoramic field of view for virtual and augmented reality. Innovega Inc., which is supported by the Defense Advanced research Projects Agency, National Eye Institute of NIH, and National Science Foundation, has a patented platform eMacula(R) that includes eyewear and iOptik® high resolution smart contact lenses that work together for applications in medicine, augmented reality and virtual reality. The FDA De Novo process Phase II clinical trials are in progress for the iOptik contact lens.41

Medella Health, yet another company whose founding team includes a Thiel Fellow, develops smart contact lenses that monitor analytes such as glucose levels, calcium, sodium, ascorbic acid, uric acid, lysozyme or IGE; and can provide a correlation between tear fluid and other blood biomarkers, enabling patients to better manage their health. It continuously and non-invasively monitors health indicators and transmits the data to a mobile phone.10 It has also filed a patent application (CN106793943) for the technology.

The Swiss Federated Institute of Technology in Lausanne also has developed telescopic contact lenses that let the user zoom in on certain objects.10

Wirelessly powered contact lens

The use of wireless powering of the contact lenses would help overcome the drawbacks associated with wired systems such as limitation in continuous use and/or the need for energy storage devices. A few approaches could be through the use of a super-capacitor, solar power or by mere blinking of the eyes.

Super-capacitor-based wirelessly powered contact lenses:

Researchers at the Yonsei University of Seoul have developed a new type of robotic contact lens that can be recharged wirelessly.42 These devices are built around a circular translucent antenna and super-capacitor system that can receive continual power without the need to be plugged to an external power source, while also alleviating problems such as raise in temperature of the lens that can cause potential long-term harm to the user and the device.

Solar-powered contact lens:

Solar-powered contact lenses generate power from light that is harvested.

Google‘s sensor-packed smart contact lens could run on solar power.43, 44, 45 Google and Verily hold several patents related to contact lenses, with a few patents (for e.g., US9610032, US10120203) disclosing contact lenses that are wirelessly powered. These future contact lenses would not only harvest light and turn it into power, but would also provide a variety of other potential health and technological benefits. For instance, they can monitor body temperature as well as glucose, allergens, and blood alcohol levels, and also process visual images such as price tags.

InWith Corporation, which reportedly holds key-enabling IP in augmented contact lenses (for e.g., US10025118), has been at work with Bausch and Lomb for the past year to develop smart contacts. InWith plans for an Institutional Review Board approval on its first prototypes. A combination of highly biocompatible materials with 3D-flexible microelectronics embedded into molded hydrogel devices, which InWith calls “smart biology”, is reportedly expected on the market “in the near future”.10 With InWith’s technology, the augmented lens will have the ability to harvest energy from the normal blinking of the eyes, check blood sugar, and send alerts and notifications. Some of the patented technologies of InWith are Energy Harvesting from the blinking human eye to power a contact lens; defining space inside hydrogel devices such as contacts, for computer circuitry to be embedded during manufacturing; and smart cases for charging smart contact lenses in liquid medium, while not in use. According to CEO Hayes, this opens the door to hundreds of new devices: blood chemistry for cancer and virus detection, drug delivery, and artificial organ parts with electronics for movement.46

A group of University of Wisconsin engineers, led by Professor Hongrui Jiang, has developed an extremely tiny solar cell designed to be embedded into contact lenses.47 The focus of this solar-powered contact lens will be its autofocusing ability. It is under development as a future product for an Israeli company called Deep Optics.48 The idea is based on the eye function of the elephant-nose fish. The lens uses electronic circuits and light sensors, which are powered by a solar cell, all built into the contact lens. When the sensors determine that the eye needs to focus, the chips command a small electrical current, which changes the focal length of the lens in a fraction of a second. Overcoming limitations on materials for fabricating the solar cell that has a small surface, which limits the energy input due to limited sunlight exposure, they have come up with a system that minimizes energy consumption of the device, added an energy storage unit and adopted the lateral design of the solar circuit.

Blink-powered contact lens:

Blink-powered contact lenses involve the ability to record what is viewed by the user based on their blinks – voluntary and involuntary.

Samsung has developed a technology wherein the contact lens comprises a sensor that detects biometric information of a user, and a power that transforms a dynamic energy generated by a movement of an eye part of the user into electrical energy and provides the sensor with the electrical energy that is harvested (US2018136492).

Sony’s blink-powered contact lens records everything the user sees upon request. Sony’s system uses the Nicola Tesla

Sony’s-contact-lens
blank-Sony’s-contact-lens

Fig. 9. Sony’s contact lens with ability to take pictures & record videos with a blink (Source)

technology wherein the lens will contain a picture-taking unit, a central controlling unit, the main unit along with an antenna, a storage area and a piezoelectric sensor. The lens is capable of detecting the difference between voluntary and involuntary blinks through the sensors embedded in it. When developed, the image capture and storage technology would be embedded in the lens, near the iris. Piezoelectric sensors would convert the twitches of the eye into energy to power the lens. Simple piezoelectric sensors would allow the movements of the eye to charge the battery of the device. The recording is turned on and off with the user’s blink and sensors can detect if it was intentional or unintentional. The image capture technology and data storage would be held within the lens.49, 50, 51. Sony also has a few patent applications (for e.g., US2016299357, US20160097940A1) related to smart contact lenses with storage medium that can adjust the light passing through the contact lens.

EP Global Communications Inc (EPGL), in addition to AR graphics and data display via onboard flexible circuitry (for e.g., US2017235158, US2018129049), is reportedly investigating methods of harvesting energy generated by the blink of an eye, and installing autofocus mechanisms and sensors directly into silicone hydrogel substrates, among other cutting-edge technologies. It announced a contact lens case which could charge the smart contact lens overnight, and transfer and analyze the measured data.35

Researchers at the University of California have developed a robotic telescopic contact lens that would allow the user to zoom on objects of interest by blinking (US9063352). The contact lenses are powered by five electrodes that are placed around the eye on the user’s face and would alter the focal length of its lens in accordance with the changes in the eye muscles, which are detected by the electrodes.52

Transition contact lenses and other Smart contact lenses:

Generally, bright lights can make a dramatic difference to contact lens wearers and their vision. Transition contact lenses quickly and seamlessly adapt to changing light and provide all-day soothing vision. Acuvue – a brand of Vistakon, a subsidiary of Johnson & Johnson, released their new Acuvue OASYS in 2018, with Transition lenses, allowing the user’s eyes to adapt to changes of light.10 These smart lenses also block harmful UV rays and blue light that come from mobile phone, laptop and tablet screens, thus preserving the health of the eyes. Its product “ACUVUE (senofilcon A) Soft Contact Lens Multifocal” has received FDA pre-market clearance recently (March 17, 2020). They hold a few patents (for e.g., US9690115B2) related to such contact lenses.

As with any device, it is important to check on the safe use of the contact lenses. Hence, incorporating failsafe features in contact lenses would add value to the product. Verily Life science LLC has come up with a technology for a failsafe operation of eye-mountable device (US10317702). The failsafe subsystem causes the device to transition to a failsafe mode upon identification of a failure condition for the device. The failsafe mode includes setting the vision accommodation state to be the failsafe focal distance.

Providing better night vision abilities has also been the focus of some researchers. The focus of the University of Michigan has been on graphene that can be embedded in smart contact lenses53 to create an image sensor that can capture light up into the mid-infrared range. This is expected to put thermal vision technology into contact lenses, which would allow soldiers to see better at night, allowing them to sense humans, animals and devices such as mobile phones through the heat they produce. Although there are infrared detectors already in use, these thermal contact lenses would eliminate the need for carrying around large and bulky cooling equipment.

With increasing demand for personalization of products, smart contact lenses have been conceptualized based on the change of color of dyes upon exposure to ultraviolet radiation from sunlight. The dyes are applied onto the contact lenses, which would enable personalized UV-protection advice. The smart contact lenses can change color when exposed to sunlight and help the user sense the color change in the user’s line of vision.

Though a lot of research on smart contact lens has been in progress, there is a dearth of commercial products in the market, probably due to the expensive fabrication techniques, difficulty in the fabrication of tiny, curvy structures with embedded micro-optoelectronics, and lack of accuracy and consistency in bulk fabrication, amongst other reasons54. Particularly, fabricating a wireless-powered circuit on a moist, soft contact lens is quite challenging. Also, it is essential to have a contact lens that is soft, flexible, biocompatible, oxygen-permeable, and optically transparent. Issues with materials used and the ability to integrate sensors onto the curved surface of a soft contact lens platform represent challenges that are to be overcome before research can translate to clinical practice.

Conclusion:

Several companies are involved in research to develop intraocular smart lenses that would surgically replace existing lenses. They are expected to retain the features of the smart contact lenses while also improving the vision of the user. Smart lens technology in the future could let the user take photographs with their eyes or monitor various body parameters to aid in early detection and treatment of diseases.

Potential exists for technologies that would help experience augmented reality through contact lenses, allowing users to display images, play videos and open web browsers right in the line of vision. From the innovative developments taking place in smart contact lens technology, it appears that smart contact lenses might soon replace smart phones in the not-too-distant future.

References
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  3. https://www.massdevice.com/googles-verily-spikes-glucose-sensing-lens-project-with-novartis-alcon/
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Dr. P. Lakshmi Santhi
Mr. N. Sai Kumar
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