Age-related macular degeneration (AMD) is a wily foe of elderly people, snatching their central vision needed to see details straight ahead – without first showing any early symptoms. 

Prof. Yossi Mandel (Bar Ilan)

The chronic and so-far incurable eye disease is the leading loss of vision loss in people aged 50 and above, making it difficult or even impossible to read, see faces, drive, perform close talks such as cooking or carry out other daily functions. Individuals are at higher risk if they smoke, are Caucasian, do not exercise regularly, eat unhealthful foods, suffer from untreated high blood pressure and high cholesterol levels and have a family history of AMD. 

While people with “early AMD” cannot benefit from treat, those with a type of “late AMD” that is called “wet” or neovascular AMD can undergo treatments to stop further vision loss, such as photodynamic (laser) treatment or anti-VEGF drugs injected into the eye. Having low central vision can be relieved somewhat with certain devices and rehabilitation programs. 

But now, researchers at Bar-Ilan University in Ramat Gan near Tel Aviv and at Stanford University in California offer some hope. They have found that the brain can combine natural and artificial vision (retina implants) to help treat AMD. 

Located inside the eye, the retina contains light receptors (photoreceptors) that absorb light, and then data is processed and transmitted to the brain. The macula – the central area of the retina – processes most of the information that reaches the brain from the eye, enabling you to carry out any activity that requires accurate vision.  In the peripheral retina – the area of the retina outside the macula that assists mainly with spatial judgment – vision is 10 to 20 times less exact.  In AMD, precise vision is impaired due to damage to the center of the retina, while peripheral vision remains normal.  

When there is damage to the photoreceptor layers in the retina, an artificial retina – a device built from tiny electrodes smaller in width than a hair – may be implanted. Activating these electrodes results in electrical stimulation of the remaining retinal cells and brings about partial vision restoration. AMD patients implanted with an artificial retina possess a combination of artificial central vision and normal peripheral vision, a combination that is important for scientists to understand how to help the blind. One of the critical questions in this regard is whether the brain can integrate artificial and natural vision properly.

In the new study published in the journal Current Biology, the Israeli and American researchers report for the first time the discovery of evidence indicating that the brain knows how to integrate natural and artificial vision, while maintaining processing information that is important for vision. 

“We used a unique projection system tjat stimulated either natural vision, artificial vision or a combination of natural and artificial vision, while simultaneously recording the cortical responses in rodents implanted with a subretinal implant,” said Tamar Arens-Arad, who conducted the experiments as part of her doctoral studies. The healthy peripheral retina is stimulated by natural light with the implant, which is  is composed of dozens of tiny solar cells and electrodes and was developed by Prof. Daniel Palanker at Stanford.

“These pioneering results have implications for better restoration of sight in AMD patients implanted with retinal prosthetic devices and support our hypothesis that prosthetic and natural vision can be integrated in the brain,” said Prof. Yossi Mandel, head of Bar-Ilan’s ophthalmic science and engineering lab and the study’s lead author. The results could also have implications for future brain-machine interface applications where artificial and natural processes co-exist,” 

Source: Israel in the News