Research Projects

Eyes are vital sensory organs in humans that enable the perception of visual information. Blindness can occur if any step in the visual pathway—from the detection of light by photoreceptors to the processing of signals in the visual cortex is disrupted. This disruption can result from damage, degeneration, or malfunction of neurons at any point along the pathway, including the retina, optic nerve, or brain regions involved in vision. Diseases like age-related macular degeneration (AMD) and retinitis pigmentosa (RP) are the most common diseases in elderly individuals, and they cause progressive degeneration of the retina. In both conditions, patients loose photoreceptors. Different types of mechanisms, like gene therapy, drug therapies, have been tried, but they have their disadvantages; therefore, researchers are investigating the possibility of using prostheses to restore vision. Advances in microtechnology have introduced the development of many types of prostheses that can be connected to the brain, as in a cortical implant, or implanted in the eye, epiretinal (on the surface of the retina), or subretinal (under the retina) implants. Retinal implants aim to successfully bypass damaged photoreceptors by electrically stimulating the remaining viable bipolar cells or ganglion cells in the retina. Subretinal implants: They contain micro-photodiodes attached to microelectrodes. The photodiodes are then stimulated by light passing through the retina electric current generated in the diodes gets transferred to adjacent retinal sensory neurons, mainly in bipolar cells. They don’t require an external electric source for the stimulation of bipolar cells. Epiretinal implants: It is implanted between the vitreous and internal limiting membrane. The implant has no light-sensitive element, but they have other mechanisms to stimulate the ganglion cells. In this device, a camera is positioned outside the eye or within an intraocular plastic lens that replaces the eye lens. The captured visuals are sent to the video processing unit (VPU), where the transmission is then converted into electrical impulses, which will be sent to electrode arrays to directly stimulate ganglion cells or axons of ganglion cells, which unite to form the optic nerve. The most important area to focus on retinal prostheses is the design of electrodes and improving the ability to stimulate the retinal cells, which are capable of eliciting recognizable phosphenes, so that patients can perform normal daily tasks. Some electrode designs have already been studied for their ability to stimulate the ganglion cells, but most of these studies were conducted on planar electrodes that were placed above the retina. We will study the effect of different 3D geometrical (non-panar) penetrating electrodes.