According to an experiment conducted with rats, the brain would be able to properly combine natural vision and an artificial retinal implant. Ultimately, this discovery offers new perspectives to people suffering from macular degeneration (AMD).
In the West, age-related macular degeneration (AMD) is the leading cause of blindness in people over 50 years of age. In Europe it affects more than 67 million people, a figure that is expected to increase significantly over the next 20 years due to the aging population. Depending on the clinical form (dry or wet) and the stage of the affliction, its manifestations may be discrete: decreased visual acuity, reading difficulties, slight deformation of some objects. At a more advanced stage, the patient will suffer from distorted vision and black spots will appear in the central visual field.
Today, a new study published in the journal Current Biology offers patients new hope. Although neurobiologists did not know whether the brain could adequately combine natural vision with an artificial retinal implant, it was found that it could.
Inside the eye, the retina captures light. The information is then processed and transmitted to the brain. In the center of the retina, the macula processes most of the information very precisely. The peripheral area helps spatial judgment with ten to twenty times less accurate vision. In AMD, accurate vision is compromised because the center of the retina is damaged. An artificial retina, a device consisting of small electrodes, can therefore be implanted. The electrodes cause electrical stimulation of the remaining retinal cells and restore normal central vision. Therefore, normal central vision is stimulated by artificial light, while the peripheral retina is stimulated by natural light.
Implications for better vision restoration
Here the researchers wanted to understand whether the visual cortex could respond in the same way to these two simultaneous stimuli. Therefore, they studied the cortical interactions between prosthetic vision and natural vision, based on the visual potentials recorded in rats implanted with photovoltaic subretinal implants.
“We used a unique projection system that stimulated natural vision, artificial vision or a combination of natural and artificial vision, recording cortical responses in rodents implanted with a subretinal implant,” explains Tamar Arens-Arad, of the University of Bar-Ilan (Israel), who conducted the studies. The implant was developed by Professor Daniel Palanker of Stanford University.
The brain is able to integrate natural and artificial vision, while retaining the necessary processing information. “These revolutionary results have implications for better vision restoration in AMD patients implanted with retinal prostheses and support our hypothesis that prosthetic and natural vision can be integrated into the brain.
The results may also have implications for future brain-machine interface applications where artificial and natural processes coexist,” concludes Yossi Mandel, head of the Laboratory of Ophthalmic Science and Engineering at Bar-Ilan University.
In response to the increasing spread of the disease, research on AMD is constantly advancing. By March 2018, researchers in the United Kingdom and the United States had managed to restore sight to patients who could no longer read, even with glasses on. During the operation, they used embryonic stem cells to produce macular cells and transplanted tissue into patients. Since then, patients have been able to read 60 to 80 words per minute with traditional reading glasses.
TAMD frequency increases with age: while it affects 1% of people aged between 50 and 55, it rises to 10% among people aged between 65 and 75 and 30% among people over 75.
If your parents or siblings have this disease, consult an ophthalmologist from the age of 50 for an examination. In addition to the genetic factor, smoking and sunlight can also increase the risk. If you are in doubt about the distortion of vision in a straight line, do not hesitate to make an emergency appointment: in 80% of cases blindness can be prevented or cured if treated in time.