The retina is a complex tissue layer located at the back of the eye. These contain light-sensitive photoreceptors called rods and cones responsible for vision.
What retina does that it converts the light rays into impulses that travel through the optic nerve to our brain. It is here where they are interpreted as the images we see.
Retinal degeneration caused by genetic mutation leads to serious disorders, including age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa. This basically results in vision impairment or complete vision loss to millions worldwide.
ARTIFICIAL RETINAL IMPLANT TO THE RESCUE
Scientists from the Italian Institute of Technology have developed and validated a retinal implant to substitute damaged retina. Moreover, this was found to restore vision in visually impaired rats.
Using Royal College of Surgeons rat model, an experimental model of retinitis pigmentosa, they revealed that the surgical implantation of the fully organic device in the sub-retinal space can restore and maintain the vision for up to 6-10 months following surgery.
The multi-layer implant comprised a surface layer of semi-conductive polymer, an intermediate layer of conductive polymer, and a flexible and comfortable silk substrate.
Upon receiving light through the pupil of the eye, this artificial retina converts light into electricity using semi-conductive polymer. Furthermore, this activates residual neurons in the degenerated retina to restore vision.
However, the exact mechanism of action of the implant remains unclear, as mention by the scientists.
To test the activity of implant, scientists evaluated pupillary light reflex, an index of light sensitivity, using light stimuli with various intensities. Thirty days post surgery, rats with implantation gained full pupillary reflex, which is identical to their healthy counterparts.
RETINAL IMPLANT RESTORES VISION IN RATS
Thirty days post surgery, rats with implantation gained full pupillary reflex, which is identical to their healthy counterparts.
Reassessment of visual activity at six and ten months post surgery ensured long-term restoration of vision by the organic implant. Moreover, the placement of implant has
Moreover, the placement of implant has a significant impact in gaining vision, as claimed by the scientists.
Restoration of vision by this biocompatible organic implant entirely depends on the properties of polymeric layers and not due to any secondary trophic effects of the implant, as indicated by the scientists.
Using positron emission tomography, scientists found that restoration of visual activity is significantly associated with elevated metabolic activity of the primary visual cortex, a brain area responsible for processing visual information.
WHY IS IT BETTER?
Previous approaches to restoring vision using prosthetic implantation in animals mostly suffer from compatibility mismatch with soft retinal tissue. In addition to that the complexity of manufacturing, and mode of operation also leads to rejections.
Additionally, such implants often need trans-ocular cables to connect with external power supply or camera, which further restrict their use as effective interventions
This new device is equipped with organic materials to avoid compatibility mismatch. The photosensitive implant can function autonomously without any need for external electricity or camera, adding extra benefits in its implementation as a therapeutic intervention.
“This is definitely a game changer,” says Kapil Bharti, an investigator at the National Eye Institute in Bethesda, Maryland.
He further adds, “Previous versions of these work in a very, very low-resolution range. Patients were practically still blind and incapacitated as far as everyday tasks were concerned. These promise that patients could become more independent.”
Considering the exciting results of the present research observed in rats, scientists are now looking forward to extrapolating the study in humans.
“We hope to replicate in humans the excellent results obtained in animal models,” says Grazia Pertile, one of the researchers and ophthalmologist from the Sacred Heart Don Calabria in Negrar, Italy.
Clinical trial, which is set to begin this year, can bring hope to million people suffering from retinal degeneration and associated vision impairments.
“We plan to carry out the first human trials in the second half of this year and gather preliminary results during 2018. This implant could be a turning point in the treatment of extremely debilitating retinal diseases,” says Grazia Pertile.
The details of fabrication, implantation, and validation of the prosthesis can be read here in Nature Materials.