Ultra-thin retina implant uses near-infrared to stimulate the retina

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A novel retina implant aims to restore vision signals using near-infrared light. Behind this is an international research team led by Prof. Dr. Sedat Nizamoğ;lu from Turkey's Koç University. As the scientists report in the journal Science Advances, the technology works without cables and external electronics. This makes it significantly more compact than previous approaches.

The implant is intended to one day help people with degenerative retinal diseases such as macular degeneration or retinitis pigmentosa. Millions of people worldwide suffer from these conditions, for which there is currently no curative treatment. Previous retina implants mostly work with high-intensity visible light and require extensive electronic components, which carries risks for the sensitive eye tissue.

Nanostructures convert light into electrical impulses

The new technology is based on photovoltaic zinc oxide nanowire arrays combined with colloidal silver-bismuth sulfide nanocrystals. These nanostructures convert near-infrared light directly into precise electrical impulses that stimulate the remaining neurons in the retina. Near-infrared light penetrates tissue deeper than visible light and is considered safer because it operates at lower intensities, which are below the safety limits for the eye. Specifically, the nanoassembly achieves charge injection densities of several tens of microcoulombs per square centimeter at NIR intensities below 1 milliwatt per square millimeter.

The nanocrystals used are chemically related to those for which the Nobel Prize in Chemistry was awarded in 2023. The study shows that a nanotechnological retina implant approach could potentially restore vision in people who have lost their sight due to macular degeneration and retinitis pigmentosa in the future. This opens up new avenues not only for visual prostheses but also for other biomedical applications in the field of neuromodulation, such as for the brain, heart, and muscles.

Tests show stable nerve cell responses

The team evaluated the technology with rat retina models with vision loss. The experiments showed strong, repeatable, and temporally precise responses in the retinal neurons. Importantly, the researchers observed no cell stress, toxicity, or temperature increase in the tissue. The implant proved to be biocompatible and stable in the long term.

Compared to existing approaches, the technology offers several advantages: the active layer is ultra-thin, the system works completely wirelessly and without external electronics, and it uses near-infrared instead of visible light. However, the work is still in the research stage – there is still a long way to go before clinical trials in humans. Other projects such as the PRIMA implant or approaches from Stanford University and the USC Roski Eye Institute are already further along and are partly conducting clinical trials.

Risk of support discontinuation

Despite all the euphoria about technical progress, a fundamental problem remains: the long-term support of such implants. In the past, patients with the Argus-II implant from Second Sight experienced that their device was no longer supported after the manufacturer's insolvency. This raises the question of how the long-term care of implant recipients can be secured – a regulatory gap that has still not been closed.

Current research on retina implants is diverse: while some teams, such as researchers from the Netherlands and Spain, directly stimulate the visual cortex in the brain, others rely on photovoltaic approaches like the international team around Nizamoğ;lu. Developments such as near-infrared contact lenses for night vision or 3D-printed corneas show how broad the research in the field of ophthalmology is.

(vza)