Findings from a study published in Nature Communications evaluated the efficacy of a novel smart contact lens (SCL) design utilizing radio frequency (RF) tags to detect and track eye movement.
Give me some background.
SCLs are an emerging technology that offer a broad variety of innovative capabilities, such as monitoring physiological changes (like tear glucose levels), drug delivery, color deficiency correction, and corneal cell repair.
There is a growing interest in using SCLs for eye tracking, as this can provide insights for analyzing visual attention and underlying cognitive processes through eye movements.
However, there are limitations to existing eye-tracking technology—namely environmental light interference in pupil corneal reflection and low accuracy in electrooculography (EOG).
Why does eye tracking sound familiar?
The Apple Vision Pro, which became available for purchase in February 2024, features eye-tracking technology for spatial computing calculations.
Talk about the SCL design.
The novel SCL used in this study was biocompatible, imperceptible, and had a frequency-encoding design to allow for in situ eye tracking and wireless eye-machine interaction.
The frequency-encoding design featured four passive RF tags—called RF identification (RFID) chips—encapsulated by silicone elastomer, each with different working frequencies.
A portable sweeping-frequency reader was installed in the framed glasses, opposite to the user’s eyeball that collected the RF tags’ signal wirelessly.
Tie this all together.
As the eye moved, the RF tags changed position, altering the signal’s frequency and allowing the device to track eye movement in real time—without the use of a battery or conventional silicon chip.
Now this study.
To assess the efficacy of the novel SCL design and observe ocular behavior (i.e., eye movement and closure) researchers:
- Utilized a 2D eye movement model to characterize the SCL’s responsiveness
- Developed an eye-tracking algorithm to perform eye calligraphy and eye painting
- Completed eye-machine interaction experiments with an eyeball model wearing the SCL that received eye command inputs
- Evaluated cytotoxicity in human corneal epithelial cells
- Performed in vivo eye-machine interaction and biocompatibility testing on rabbits
- This included using the rabbits’ eye movements to drive a robot vehicle
Findings?
Utilizing the eye tracking algorithm, they found that the lens had a high angular accuracy (<0.5°)—which is even less than the vision range of the central fovea.
In the eye movement model and in vivo rabbit models, they demonstrated multiple eye-machine interaction applications, such as:
- Eye-drawing
- Gluttonous Snake game
- Web interaction
- Pan-tilt-zoom camera control
- Robot vehicle control
Anything else?
The comprehensive biocompatibility tests performed on the SCLs demonstrated low cytotoxicity and eye irritation.
The SCL also performed well in responding to:
- Ambient light
- Common electromagnetic interference
- Different wearing angles
- Varying corneal curvatures
- Slightly varying reading distances
Expert opinion?
Fei Xu, PhD, corresponding author of the study, stated, “With the development of optoelectronic technology and the improvement of the flexible integration of optoelectronic devices, contact lenses will realize more and more functions in human-computer interaction and medical health.”
He added that SCLs also offer great potential for innovation in augmented reality (AR) as they allow for the seamless integration of the virtual and real world.
Take home.
These findings indicate that this novel, wireless SCL design could enhance current approaches to eye tracking and improve the development of ophthalmic wearable devices.
Next steps?
The study authors mentioned potential avenues for improving the SCL design, such as:
- Increasing flexibility and transparency using highly conductive transparent electrodes
- Optimizing the structure of the smart device
- Integrating field cameras and sensors to achieve intelligent eye-tracking applications