Age-related macular degeneration (AMD) and retinitis pigmentosa are major causes of vision loss. Worldwide, AMD affects approximately 200 million people, and retinitis pigmentosa 1.5 million people.
In both conditions, there is a reduction in the sensitivity to light of retinal photoreceptors; however, certain retinal neurons such as bipolar and ganglion cells remain functional. This has sparked interest in research aimed at restoring vision.
A study conducted by researchers at Brown University in the United States points to a new type of visual prosthesis system that combines the use of plasmonic gold nanorods with a small laser device integrated into eyeglasses.
The researchers injected gold nanorods into the vitreous humor of mice eyes, where the particles incorporated into the retina and into bipolar and ganglion cells. A scanning laser with wavelengths in the near-infrared region of the visible spectrum and a beam size of 20 microns was then used to focus infrared light onto the nanoparticles, generating a small amount of heat that activated the bipolar and ganglion cells. This activation pattern mimicked the natural visual signals processed by the brain through photoreceptor pulses.
Laser stimulation led to increased activity in the visual cortex of the mice indicating that previously absent visual signals were being transmitted and processed by the brain.
The study found no signs of toxicity or inflammation over several months.
This finding suggests the potential application of a similar technology in humans. The use of near-infrared light, rather than visible light, is non-invasive and does not interfere with residual vision that the patient may still retain. Although further testing is needed before clinical application, the findings point to a less invasive option for vision restoration.
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