A team of South Korean researchers recently presented a wearable, non-invasive bioelectronic platform that uses contact lenses for the first time to treat a brain disorder. Tested on mice, the device produced results comparable to fluoxetine — the active ingredient in Prozac.
Without using surgery or any type of medicationthe platform takes advantage of the eye as a gateway to the brain. As it is, anatomically, an extension of brain tissue, the retina functions as an access route to regions linked to mood regulation, such as the hippocampus and the prefrontal cortex.
According to the study, the lenses use the principle called temporal interference, which combines two high-frequency — but harmless — electrical signals that are found on the retina and generate a low-frequency field there that activates neurons and propagates the signal throughout the brain.
The lenses are manufactured with ultra-thin platinum and gallium oxide electrodes, materials chosen because they are transparent and flexible enough to adapt to the surface of the eye without compromising vision. The entire stimulation structure is integrated into a single malleable lens.
Safety assessments performed on animals did not detect structural damage to the cornea or retina, nor signs of inflammation or cell death in ocular tissues. The researchers exposed laboratory-grown human cornea to the liquid in which the lenses were immersed, and 99.25% of the cells remained alive after 24 hours.
Testing Transcorneal Electrical Stimulation in Mice
To test the temporal interference transcorneal electrical stimulation (TI-TES) technique, researchers induced depression in mice with injections of corticosterone — a stress hormone — and divided the animals into four groups: healthy control, untreated, treated with the lenses and treated with fluoxetine.
After testing with 36 different combinations of frequency, intensity and duration, the researchers stimulated the animals in daily 30-minute sessions for three weeks, with signals of 20 Hz and amplitude of 200 mV. The group treated with daily injections of fluoxetine followed the same schedule.
Observing the animals released in arenas, suspended by the tail and placed in containers with water, the authors noticed that those treated with the lenses showed 76% more locomotion, 132% more time in open areas and around 45% less immobilitywhen compared to the untreated group.
Biological biomarkers confirmed the behavioral improvement: and the BDNF protein, essential for synaptic plasticity, was restored by 131% compared to the depressed group. Inflammatory markers in the hippocampus decreased significantly.
AI validates results and points to new treatments
To analyze the results objectively, the researchers applied machine learning to the integration of behavioral, electrophysiological and biological data from the animals. The algorithm classified the mice treated with the lenses into the same group as the healthy ones.separating them from the untreated depressed group.
Electrophysiological recordings showed that the loss of synchronization between the hippocampus and prefrontal cortex — a circuit often compromised in depression — was recovered after three weeks of stimulation. This restoration of connectivity was one of the most relevant findings of the study.
The authors’ expectation is that, in the future, the technology can be adapted — by adjusting the type of stimulus applied — to other brain disorders, since the retina connects to different circuits of the brain.
In a press release, study senior author Jang-Ung Park, a materials scientist at Yonsei University, says: “We plan to make the lens completely wireless, test it for long-term safety in larger animals, and personalize stimulation for each user before moving into clinical trials in patients.”
