An ocular prosthesis restores sight to people with irreversible blindness.

A new ocular prosthesis has successfully restored vision to people with irreversible blindness due to geographic atrophy, the final stage of a form of age-related macular degeneration (AMD) that affects approximately five million people worldwide. An international team of European and American scientists has been working on the development of this device for two decades , successfully testing it in a trial with 38 patients at 17 hospitals in five countries. Their results were published this Monday in the New England Journal of Medicine .

The 32 patients , all over 60 years old, suffered from the aforementioned geographic atrophy caused by age-related macular degeneration, a condition, currently incurable, that slowly deteriorates vision. At the time of the trial, they had only limited peripheral vision. One year after having the device, called Prima, 27 of the 32 participants (84%) regained the ability to read letters, numbers, and words with the eye that had lost sight.

A wireless photovoltaic microchip

Prima is a two-part device: a wireless microchip implanted in the back of the eye and augmented reality glasses. The microchip is ultra-thin, measuring two by two millimeters and shaped like a SIM card . It is placed in the eye through a procedure called vitrectomy, in which the vitreous gel between the lens and the retina is removed, and the chip is inserted beneath the center of the patient's retina.

A small camera, installed in the augmented reality glasses , captures images of the outside world and projects them in real time, using infrared light, onto the microchip installed in the eye. The chip is sensitive to the infrared light projected from the glasses and performs the functions of the natural photoreceptors that have been damaged by the disease.

The device is photovoltaic and requires only light to generate electrical stimuli, so it doesn't require external power like other previous ocular prostheses, which required some type of "cable" extending from the eye. The design allows patients to use their natural peripheral vision along with their central vision through the ocular prosthesis, helping them navigate and navigate.

"The fact that a person can see simultaneously with both prosthetic and peripheral vision is important because they can merge the two and maximize their vision," said one of the authors, Daniel Palanker, an ophthalmology researcher at Stanford University in the United States, in a statement from the center.

Phases of vision recovery

The patients began using the augmented reality glasses four to five weeks after the microchip was implanted in their eyes. While some were able to distinguish patterns immediately, most improved their visual acuity after months of training, similar to other implants developed to restore hearing.

Of the 32 patients who completed the one-year trial, 27 achieved reading, and 26 showed a clinically "highly significant" improvement in visual acuity, defined as the ability to read at least two additional lines on a standard eye chart. Participants in the clinical trial achieved visual acuity of up to 20/42 . This improvement, on average, was five lines, with some recovering by 12 lines.

Most participants use the prosthesis in their daily lives to read books, food labels, or street or public transportation signs. The glasses allow for adjustable contrast and brightness and feature a zoom capability of up to 12x magnification. According to the authors, two-thirds of participants expressed medium-to-high satisfaction with the device.

Nineteen of the 32 experienced side effects , including ocular hypertension, peripheral retinal tears, and subretinal blood collection, but the side effects resolved within two months or less and were not life-threatening, the authors report.

Next steps

For now, Prima only offers black and white vision , without intermediate tones, so researchers are developing software that will allow it to distinguish the full range of gray tones. "Participants' first desire is to read, but the next is facial recognition, and for that we need software that recognizes gray tones," Palanker points out.

He and the rest of the team are also working on chips that offer higher-resolution vision and sleeker-looking glasses. Another goal is to test the device for other types of blindness caused by photoreceptor loss. This successful human trial of the Prima device is the culmination of decades of development, prototyping, and animal experiments .