Contact lenses may soon do more than just correct vision problems. Smart contact lenses (SCLs) are a rapidly evolving technology that merges advances in material science, microelectronics, and biomedicine. They have the potential to transform how we manage health conditions and revolutionize how we interact with our daily world.
These promising new lenses aim to provide real-time biometric data and even deliver therapeutic agents, potentially empowering people to detect changes in their health earlier and manage ocular or systemic conditions more effectively.
If smart contact lenses overcome developmental challenges and achieve widespread adoption, a future in which we experience longer, happier, and more fulfilled lives could be just around the corner.
Capabilities of smart contact lenses
Since their inception in the late 19th century, contact lenses have undergone a significant evolution. From early glass and plastic designs to the breathables of today, contact lenses have continuously improved in comfort and efficacy. However, it is the integration of smart technology that promises to redefine their role in vision care.
Eye tracking
Smart contact lenses equipped with miniature sensors and electronics can enable a range of functionalities beyond simple vision correction. One surprising feature of SCLs is the ability to track eye movements, achieved through electrooculography (EOG) and pupil center corneal reflection.1
Eye movement information is ciphered into radio frequency (RF) signals via frequency encoding, using RF tags embedded within the contact lens. Similar to RFID chips found in credit cards, these RF tags are wireless and battery-free, making them ideal for eye-tracking applications. Each tag emits a unique frequency signal corresponding to different eye positions.2
As the eye moves, the relative positions of the RF tags change, altering the frequency of the emitted signal. By detecting and analyzing these frequency changes, the system can determine the direction and extent of eye movements in real time.
Eye tracking smart contact lenses could revolutionize various fields, from healthcare to sports performance. In vision therapy, these lenses could help identify and track patients with eye coordination issues, such as convergence insufficiency or strabismus.
For athletes, these lenses could help coaches and trainers develop personalized sports vision training plans to optimize hand-eye coordination and reaction times, i.e., detecting a golfer’s eye movements during a swing to identify any delays or inefficiencies. The possibilities are vast, and the potential benefits for individuals and society as a whole are immense.
Glucose monitoring for diabetes
One exciting application of SCLs is the development of tear glucose sensors, allowing patients with diabetes another way to monitor blood sugar. Diabetes management traditionally relies on invasive blood glucose monitoring, which can be inconvenient and uncomfortable for many patients.
By alternatively measuring glucose levels in tears, these lenses provide continuous real-time data to help individuals make informed decisions about their diet, exercise, and medication. Smart lenses for glucose monitoring can even be programmed to alert users when glucose levels reach critical thresholds, enabling timely interventions.
IOP monitoring for glaucoma
Glaucoma, a leading cause of irreversible blindness, is caused by retinal ganglion cell damage due to mechanical pressure.3 It is strongly associated with elevated intraocular pressure (IOP). The gold standard for IOP measurement is Goldmann applanation tonometer, however it has its limitations.
Patients are often required to routinely visit their doctor's office during daytime hours and be tested in a static and seated posture. However, eye pressure can fluctuate greatly during a 24-hour period due to activity level, body position, or circadian rhythm.4
The advent of SCLs may revolutionize this process by enabling continuous and non-invasive IOP monitoring through sensors embedded in the lenses. Proposed prototypes determine IOP by measuring subtle curvature changes within the cornea, recorded in millivolts (mV) instead of the traditional millimeters of Mercury (mmHg).
It is estimated that an IOP change of 1mmHg causes a change in the central corneal radius of curvature by 3μm.4 Developing prototypes in this field possess radio antennae, passive gauges, microprocessors, and other electronic components to make them truly wireless.5
There are four primary types of sensors used in SCLs for IOP monitoring:
- Capacitance
- Piezoresistive
- Strain gauge
- Micro-inductor sensors
Each type has unique characteristics for IOP monitoring, but can all function for long hours while maintaining comfort, transparency, and oxygen permeability for patients. These flexible, resilient devices may offer a truer picture of how one’s eye pressure changes throughout the day, regardless of whether they are active or sedentary.
By determining time under control throughout fluctuations of the diurnal curve, the management of glaucoma via IOP-lowering treatments may become more effective.
Advancements in early detection of glaucoma
Detecting early-stage glaucoma is crucial to prevent vision loss, but many patients remain undiagnosed due to the challenge of continuous IOP monitoring amidst varying temperatures. Researchers have developed a prototype smart contact lens that accurately measures IOP, regardless of temperature fluctuations.
This device, described in ACS Applied Materials & Interfaces, utilizes a dual inductor-capacitor-resistor (LCR) resonant system for temperature self-compensation. The lens incorporates compact circuitry that integrates low- and high-frequency resonators without impairing vision, employing advanced fabrication techniques to maintain accuracy despite temperature changes.
Testing on porcine eyes demonstrated the lens's ability to monitor IOP with high sensitivity and linearity, showing less than 7% deviation from true values, even with temperature variations exceeding 10°C/50°F. This innovation promises significant advancements in the diagnosis and management of glaucoma, potentially transforming continuous IOP monitoring into a reliable, all-weather capability.6,7
Medication delivery by smart contact lenses
SCLs can deliver targeted medications to the eye for conditions like glaucoma and severe dry eyes. Unlike teardrops, SCLs can precisely administer medication, reducing systemic side effects. This benefits sensitive groups, such as patients who may be pregnant, young, or immunocompromised. This also improves treatment efficacy and reduces compliance issues, whether from lack of motivation or ability.
In 2002, a meta-analysis studied patient adherence to medical advice. Patients with good compliance had two to three times better treatment outcomes than those with poor compliance, earmarking the vital importance of effective treatments with high patient compliance in any medical field.8
One of the largest opposing factors is treatment affordability, as a significant number of patients struggle to afford their medications. As demonstrated by a cohort study, 53.6% were unable to adhere to their treatment plans due to cost, leading to 23.6% permanently discontinuing their prescriptions.9 A lens material called pHEMA hydrogel offers good water permeability and compatibility with ocular tissue and is actively being researched as a vehicle for the delivery of small-molecule medications.10
In 2022, the FDA passed phase 3 trials for Acuvue Theravision, a daily disposable etafilcon contact lens infused with ketotifen. The antihistamine molecules released helped control eye allergy symptoms like itching.11,12 Although the product was available in Canada, Johnson & Johnson ultimately decided to discontinue the lens effective December 28, 2024.
However, Mediprint is another company with multiple emerging products coming down the pipe, including a weekly disposable, extended-wear contact lens to treat glaucoma.12 Using a unique printing process, this lens delivers preservative-free bimatoprost to the eye from its ocufilcon D soft hydrophilic surface. Clinical trials, SIGHT-1 and -2, showed an average 30% decrease in eye pressure with no serious treatment adverse effects.13,14,15
Drug-dispensing SCLs offer advantages over traditional eye drops in bioavailability by preventing drug loss due to blinking and tears. SCLs incorporating drug complexes and micelles have shown promise in glaucoma treatment, though challenges such as sensitivity, biocompatibility, and stability remain.
Multifunctional smart contact lenses
Beyond IOP and glucose monitoring, SCLs are being developed to measure additional physiological and environmental parameters to ensure that they remain functional and comfortable for their intended use.
For instance, a flexible method for fabricating multifunctional SCLs uses a serpentine mesh sensor system based on ultrathin MoS2 transistors. These lenses include a photodetector for optical data, a glucose sensor for blood sugar levels, and a temperature sensor for corneal diseases. The serpentine mesh shape provides high detection sensitivity and mechanical robustness without interfering with blinking or vision.5
One study developed a different flexible multifunctional contact lens utilizing an inorganic magnetic oxide nanosheet to seamlessly conform to the eyeball, enabling the simultaneous monitoring of glucose levels in tears, eyeball movement, and eye pressure.5
Another study developed a SCL to both continuously monitor glucose and treat diabetic retinopathy. This lens incorporates an ultrathin biocompatible polymer, flexible electrical circuits, and a microcontroller chip, enabling real-time electrochemical biosensing, controlled drug release, wireless power management, and data communication.
This innovative approach has shown promise in diabetic rabbit models, demonstrating the feasibility of SCLs for non-invasive, continuous diabetic diagnosis and management.
A look at Mojo Vision’s augmented reality SCLs
SCLs also have the potential to incorporate displays that superimpose information onto what the wearer sees. Over the last decade, millions in research and development have poured into augmented reality (AR)-enabled smart contact lenses.
In 2022, a company named Mojo Vision developed an augmented reality smart scleral contact lens that could be controlled by eye movement alone. They see a future where their devices can display notifications, provide navigation instructions, and enhance details of the viewed environment for its wearer.
It should be noted that, though still in development, Mojo Vision decelerated work on the smart contact lens in early 2023, shifting their focus to micro-LED technology. Their CEO, Drew Perkins, attributes this pivot to a skeptical market for advanced augmented reality products and overall challenges in raising capital.16
Figure 1: Image of the AR smart contact lens in development by Mojo Vision.
Figure 1: Courtesy of Mojo Vision.
The ultimate goal is to have these SCLs establish connections with devices, like smartphones, tablets, or computers, to allow for data transfer, real-time communication, and even the remote control of functionalities.
Mojo Vision’s prototype is equipped with:17
- The world's densest pixelated 0.5mm microLED display built in the center of the contact,
- A 5GHz radio
- Battery supply
- Multiple miniature eye-tracking sensors that are placed around the lens periphery
To keep its 15° AR image stable, this lens features the same inertial momentum unit found in smartphones to determine the users’ spatial orientation.17 Mojo designed the lens with "invisible computing" to help seamlessly integrate into the user's daily life.
This non-invasive format ensures that the information is accessible without being disruptive. Users interface with eye control through its highly sensitive eye-tracking technology. The circuitry is safely housed inside the highly oxygen-permeable polymer of a scleral lens, protecting the eye from leached materials.
This unique lens type offers high visual optics stability. Even patients with corneal irregularities and severe dry eyes are able to optimize their vision because of its ability to create a “perfect” refractive surface. A scleral lens vaults over the cornea, cushioning the eye in a reservoir of tears, and gently lands onto its scleral contours, effectively locking it in place.
Mojo proposed designs for later models to not only improve computing power and display capabilities, but also to conceal its circuitry behind a digitally printed iris with color. Additionally, smart lenses with language translation capabilities have the potential to enhance communication for individuals with language barriers, opening up new possibilities for global connectivity.
Challenges and considerations with smart contact lenses
While the future of smart contact lenses is undoubtedly exciting, several challenges and considerations must be addressed. Despite the significant advancements, several challenges hinder the widespread adoption of SCLs.
These include:
- High costs
- Technical complexity
- Need for continuous power
- Potential discomfort
- Possible eye irritation
- Regulatory hurdles
Despite the promise, developing these lenses presents technical challenges, including ensuring measurement accuracy, biocompatibility, data security, regulatory approval, and cost-effectiveness.
Risks from SCL overwear
Contact lens materials show low cytotoxicity and eye irritation contributing to their compliance. However, dry eye syndrome is prevalent among individuals with allergies, contact lens wear, diabetes, and glaucoma.18-21 While SCLs offer potential benefits for managing these conditions, compliance can be a challenge if they compromise comfort or vision.
Continuous wear of health monitoring lenses may not be practical, and overwear can actually lead to further complications. Corneal hypoxia, a common risk associated with extended wear, can cause reduced sensitivity, edema, neovascularization, and infections.22
While IOP or glucose monitoring lenses may be beneficial during waking hours, the risks of extended wear may outweigh the advantages for some patients. Optometrists play a crucial role in educating patients about proper contact lens care to minimize risks and ensure the long-term viability of this technology.
Data security in smart contact lenses
Given the sensitive nature of the biometric data collected by SCLs, ensuring data security and user privacy is paramount. Frequency encoding for eye tracking offers a secure method to protect people's iris and other biometric information without the need for a battery or chip.
Privacy will be of utmost concern if the world eventually adopts AR-enabled SCLs. These lenses have the potential to continuously record and transmit video and audio of the users’ most intimate moments without their awareness. Without the right cyber security and legal protections in place for such devices, there would be massive vulnerabilities to cybercriminals.23
Hackers looking to exploit people's lives or intellectual property draws major concerns for not only privacy but safety as well. Legislation would need to be strictly mandated to prevent major breaches in user data and protect people from falling prey to hackers or even companies from predatorial invasive marketing.
Moreover, we could face an Orwellian dystopia from an overly oppressive government. If government agencies fail to enforce and protect our privacy rights as citizens and instead grossly infringe on our personal freedoms for the sake of public safety, these could ultimately be used for population control and serve as a detriment to society overall.
The problem of SCL cost prohibitiveness
High costs may hinder the widespread adoption of smart contact lenses. The disposable nature and the potential for loss or damage could limit consumer willingness to invest in such products, as Mojo Vision demonstrated by shifting their energy away from their smart contact lens to micro-LED development after encountering funding challenges.16
This highlights the economic and technical difficulties in this field. Similarly, Verily's discontinuation of its glucose-monitoring lens project underscores the challenges in achieving reliable and consistent measurements.24,25,26 Another difficulty for SCLs is the ability to reliably monitor or treat more than one parameter at a time.
Continued research and innovation is needed for contact lenses to achieve multifunctionality. Advances in microfabrication, energy-efficient components, robust data security protocols, and regulatory frameworks will be crucial. Furthermore, fostering public trust through transparency and demonstrating the health benefits of SCLs will be essential for their acceptance and widespread use.
The future of smart contact lenses
Several advanced technologies are already available in the realm of smart contact lenses, including prototypes capable of glucose monitoring and medication delivery. However, ongoing research holds promise for even more advanced functionalities, such as real-time diagnosis and personalized vision correction.
Solving power and connectivity challenges will usher in a new era of intelligent ocular devices. Energy-harvesting devices are being researched to serve as microbatteries to power a SCL by transforming incoming light into electrical energy.5 Integrated batteries and biofuel-based power sources are also being explored. Tear-based batteries, which harness enzymatic reactions for charging, offer a promising solution for powering SCLs.
Blink Energy aims to address power issues in smart lenses with their patented BlinkIT technology, an ergonomic patch worn under the upper eyelid. This patch wirelessly energizes a display-enabled contact lens and connects to a smartphone, allowing real-time text message reading.
Blink Energy plans to use this technology for IOP and glucose monitoring, offering a comfortable design to improve compliance. Coupled with an online health monitoring app, this innovation will enable proactive health management.27
With continued innovation and collaboration between researchers, engineers, and healthcare providers, the future possibilities for smart contact lenses appear limitless. Responsible leadership from the government, big pharma, and tech companies will be necessary to help propel future research and develop these groundbreaking technologies into safe, viable products.
Conclusion
Smart contact lenses represent a significant leap forward in wearable technology and human-machine interaction by offering non-invasive, continuous monitoring and treatment of various health parameters. They also hold the potential to enhance daily life through AR interfacing.
While challenges remain, the potential benefits of managing chronic conditions like glaucoma and diabetes are immense. Continued innovation and collaboration across multiple disciplines will be key to realizing the full potential of SCLs, paving the way for a new era of personalized healthcare and precision medicine.
