A newly launched clinical trial at the Save Sight Institute and Sydney Eye Hospital is set to test the effectiveness of a new device in partially restoring vision through the electrical stimulation of the retina.

Functioning as built-in biological cameras, the retinas within our eyes consist of light-sensitive cells known as photoreceptors. These photoreceptors capture and convert light into electrical signals that are transmitted by the optic nerve to the brain to enable sight. However, in inherited retinal diseases like Stargardt disease and retinitis pigmentosa, these photoreceptors are damaged, resulting in the gradual loss of either central or peripheral vision, respectively.

An innovative system of specialised devices known as PRIMA has been developed to partially restore the vision of people with damaged photoreceptors. The PRIMA system has two main parts: the PRIMA Stim, a small electrical stimulator that is surgically implanted under the retina, and the PRIMA Companion, a pair of glasses with a mounted projection module and pocket computer.

Together, the PRIMA system works as follows: first, the mini-camera of the PRIMA Companion’s projection module records the surrounding environment. The pocket computer then translates this information into stimulation pulses that are received by the projection module. Using an infrared projector, the projection module sends the same pulses to the PRIMA Stim, which contains hundreds of electronic cells that essentially act as substitutes for the damaged photoreceptors.

Similar to what naturally happens in the eye, each electrical cell captures the projected infrared light and converts it into electrical impulses that stimulate the retina. The retina receives the impulses from the PRIMA Stim and sends this information to the brain through the optic nerve, allowing the brain to form a simplified image of the recorded environment. Though the process may seem complex, all this happens in a fraction of a second—making real-time sight a possibility.

As a new technology, the PRIMA system comes with certain limitations. For instance, each electronic cell of the system corresponds to a single pixel of the image originally recorded by the mini-camera. While a detailed image like a photograph typically consists of tens of thousands of pixels, the PRIMA system can only generate an image made up of a few hundred pixels. Therefore, any images resulting from the PRIMA system are greatly simplified.

Under the leadership of Professor Matthew Simunovic, head of the Save Sight Institute’s Retinal Disease and Rescue Group, a three-year clinical trial called PRIMAlia testing the effectiveness and safety of the PRIMA system has been launched. While the PRIMA System has already been applied in patients with age-related macular degeneration, PRIMAlia is the first study of its kind for inherited retinal diseases.

If you know anyone affected by Stargardt disease or retinitis pigmentosa and unable to read large letters, they may be eligible for the PRIMAlia clinical trial. For more details, contact Clinical Research Orthoptist Catherine Le at catherine.le@sydney.edu.au or 02 9382 7309.