Blindness affects millions of people worldwide and severely limits their independence, daily functioning, and overall quality of life. In Spain, the prevalence of blindness is estimated at 0.17% , whereas more than 43 million individuals are thought to be blind globally. Finding effective approaches to restore vision remains a major clinical and public health priority.

Researchers have evaluated visual prostheses that connect directly to the brain. New data from the Biomedical Neuroengineering group at Miguel Hernández University of Elche (UMH) in Elche, Spain, published in Science Advances, describe the early results in two individuals with complete loss of sight and outline what the cortical implant system can currently deliver.

Speaking with Univadis Spain, part of the Medscape Professional Network, Eduardo Fernández Jover, MD, PhD, director of the Institute of Bioengineering at UMH, discussed the study findings.

“We do not see with our eyes; we see with our brain. The eye captures the information, the retina encodes it and sends it to the central nervous system, and from there it reaches the visual cortex of the brain, where vision actually occurs,” he said.

Cortical Implants

The UMH system uses a small external camera mounted on conventional-looking glass to replace the retina of the eye. “We essentially bypass the retina,” said Fernández Jover. A portable computer carried in a backpack processes visual input and converts it into electrical stimulation patterns delivered to the occipital cortex via implanted intracortical electrodes.

A key innovation is that the implant does not operate in an open-loop system. Instead, it creates a bidirectional dialogue between the brain and device. “Vision is not a passive process; it is a constant exchange of information between the eye and the brain, so artificial systems must also replicate this function,” Fernández Jover said. Earlier devices only stimulated the cortex without registering how the neurones responded.

“In this study, we established a bidirectional dialogue with the brain. While generating electrical stimuli that produce visual perceptions, we simultaneously recorded brain activity and adjusted the stimulation in real time, depending on how the neurones around the electrodes responded. This system not only writes on the brain by delivering electrical patterns that evoke visual sensations but also reads neuronal responses and adapts to them in real time. The system learns from the brain, and the brain learns from the system,” he said.

Because this process relies on preexisting visual pathways, the implant is suitable only for individuals who have lost vision after having had it. “In individuals born blind, the visual cortex never develops its visual function. These areas have been reorganised for language or spatial recognition. An implant cannot ‘speak’ to a visual system that never existed,” Fernández Jover said.

The researchers implanted an array of 100 penetrating intracortical microelectrodes manufactured in Utah.

Implantation was performed using a surgical robot and an advanced neuronavigation system to ensure accuracy without the need for open cranial surgery. UMH developed the software, hardware, and signal-processing tools for the system.

Two men with irreversible bilateral optic neuritis and complete lack of light perception were enrolled in the study. One participant, aged 64 years, had been blind for 2.5 years, whereas the other, aged 61 years, had been blind for 16 years. Both participants exhibited good cognitive function and functional abilities, with no underlying health issues.

Patient selection was one of the most challenging steps in this study. “They had to be in good physical health because the process requires implantation and explantation at 6 months, and there is a risk of epilepsy. They also needed good mental health because after the project and improvement in their functional vision, they had to return to their original state, which can be difficult psychologically. They were informed that they were participating in a research project and were not receiving a clinical intervention. The benefits would not be for them but for future patients with similar conditions. This meant that we excluded 98% of interested volunteers,” Fernández Jover said.

Only one participant could be implanted at a time because each person had to remain on the UMH campus throughout the 6-month study period for continuous testing. The aim was to reach a total of five participants.

Results

Both participants with implants were able to recognise complex patterns, movements, shapes, and letters. Fernández Jover emphasised the need for realistic expectations: “It is particularly important not to create false expectations. The goal today is not for individuals to see again as before but to recover a functional form of vision that becomes gradually less limited and gives them more independence.”

Another important finding was that neuronal activity recordings allowed the prediction of whether electrical stimulation would produce a visual percept, its relative brightness, and the number of percepts. This capability enables the dynamic adjustment of stimulation parameters, improving adaptation and speeding the learning curve.

Path to Clinic

Researchers have noted that although these results are promising, substantial work remains before such a device can be used clinically. “There are still many problems to solve, so we must advance slowly and avoid false expectations,” said Fernández Jover. “Just as hearing aids do not restore normal hearing, these systems will not restore normal vision, but in the medium to long term, they could provide functional vision that greatly improves independence.”

For individuals born blind, he added, “Their case is much more complicated because they do not have any visual system. However, the brain is a powerful data-processing machine with enormous plasticity; therefore, a prosthesis could be developed for patients in the long term. But this is only a hypothesis; we must wait.”

The authors reported having no relevant conflicts of interest.

This story was translated from Univadis Spain.