One great thing about being the Gulden Ophthalmics blogger is learning about vision research that is taking place in the U.S. and around the world. It is good to know that with all the negative happenings in the world that there are people who are working diligently to both improve vision and reduce the incidents of blindness in those who have conditions like macular degeneration.
Speaking of which, there are two research projects that use bionic and biologic means to improve vision in persons who have macular degeneration.
Staring with the bionic research, work done at the lab of Daniel Palanker, PhD, professor of ophthalmology at Stanford University School of Medicine led to the implantation of a 1/12-inch pixelated chip at the back of a patient’s eye who had macular degeneration. The chip works with specially designed glasses and it was found that the patient had partial vision restored.
This is an important development since current treatments slow the visual decline but can’t stop degeneration or restore sight. The Palanker’s team developed the glasses with a video camera that work with the chip. The camera transmit images to the chip in the eye and a near-infrared display on the glasses beams a video stream to the chip. This light activates the chip and the chip acts like a photoreceptor, which sends visual information to the brain.
Palanker and his colleagues recruited five patients who were over the age of 60 and had advanced macular degeneration with no photoreceptors in the central macula. Yet, they did have inner retinal nerve cells that were able to receive signals from the implant. The chip was inserted under the blind spot of the retina. A few months after the surgery, the implant helped patients to sense light and see patterns project from the camera. In a follow up study, the remaining three patients’ (one had the chip inserted incorrectly and another died of causes unrelated to the implant) vision was able to integrate the prosthetic central vision with their remaining peripheral vision. The visual acuity of this prosthesis is 20/460, which lets patients see large letters. His team is working on an implant that will provide visual acuity that may exceed 20/100.
What about the biologic research? You ask. Well, scientists at University of Wisconsin School of Medicine and Public Health have shown that a retinal cell developed from human pluripotent stem cells is able to detect light and convert that signal to electrical waves.
This is the first time that cone photoreceptors derived from stem cells were able to respond to light and this could lead to new ways to treat vision loss. In fact, retinal organoid could serve as a replacement source for photoreceptor cells.
According to study co-author, David Gamm, MD, PhD, the retinal organoids have the correct cell type and necessary structures to function, yet it was uncertain if they could detect light. He and co-author, Raunak Sinha, PhD used advanced electrophysiological techniques to analyze the cells electrical activity and they found that the cells responded to light in similar way to cells in the human fovea.
“The cells responded robustly, and could differentiate between red, green and blue light, just like in normal human cones. It’s really quite remarkable” said Gamm. He and Sinha are now working on improving the organiods electrical responses, in order to bring them closer to the performance of the human fovea. The hope is that this could lead to treatments that will help patient with macular degeneration and other conditions that lead to blindness regain their sight.
Not only did I learn something about these two projects, I’m sure you did, as well.