An antidepressant contact lens with effectiveness comparable to that of conventional antidepressant drugs has been developed. Electrodes embedded in the lens stimulate the brain to alleviate depression.

A research team led by Professor Jang-Woong Park of the Department of Materials Science and Engineering at Yonsei University developed contact lenses capable of delivering weak electrical signals to the brain via the retina to stimulate brain regions associated with depression, and published the findings in the international journal “Cell Reports Physical Science” on the 14th (local time). While smart contact lenses already exist to measure intraocular glucose concentration or intraocular pressure to monitor ophthalmic or metabolic diseases, this is the first time contact lenses have been used to treat brain disorders.

Current methods for treating depression include medications such as selective serotonin reuptake inhibitors (SSRIs), electroconvulsive therapy (ECT), and brain-implanted devices. These are therapies that target brain regions involved in mood regulation.

Focusing on the fact that some brain regions related to mood regulation are connected to the retina, the research team tested whether brain stimulation would be possible using contact lenses. Because the eye is anatomically considered part of, or an extension of, the brain, they viewed the eye as a potential non-invasive pathway to stimulate the brain.

The contact lenses developed by the team stimulate the brain using a method called “temporal interference.” When two electrical signals are delivered to the retina, only the point where the two signals intersect becomes activated, allowing specific brain regions to be targeted. Park explained, “If you overlap two flashlights, a bright light forms at a spot distant from the flashlights,” adding, “Similarly, two electrical signals emitted from the contact lens overlap deep inside the eye and can stimulate brain regions associated with mood.”

The research team fabricated electrodes using ultra-thin layers of gallium oxide and platinum, designing the contact lenses to be flexible and transparent. In animal experiments, they confirmed that the developed contact lenses reduced depressive symptoms from behavioral, neurological, and physiological perspectives.

The team measured behavior, brain activity records, and depression-related biomarkers in blood and brain tissue in four groups: an untreated depression rat model, a depression rat model that received temporal interference stimulation, a depression rat model administered fluoxetine (the active ingredient in an SSRI), and a non-depressed control group.

Rats that received 30 minutes of temporal interference stimulation per day for three weeks showed behavioral improvements comparable to those administered fluoxetine. Brain activity records showed restoration of connectivity between the hippocampus and prefrontal cortex, which had been impaired by depression. Levels of stress hormones decreased, while levels of so‑called “happiness hormones” increased, indicating partial recovery of depression-related biomarker levels.

Park said, “The contact lens treatment improved behavior, brain activity, and biological indicators together, and showed effects similar to widely used antidepressants,” adding, “Wearable, non-pharmacological treatment approaches are expected to have potential not only for depression but also for a variety of brain disorders such as anxiety disorders, drug addiction, and cognitive decline.”

To apply the contact lenses developed by the team to humans, they must undergo rigorous clinical evaluation. As follow-up research, the team plans to test long-term safety in larger animals and develop personalized stimulation protocols for individual users, moving toward clinical trials in patients.

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