USC Roski Eye Institute Researchers Discover Way to Improve Image Sharpness

Retinal implants that deliver longer pulses of electrical current may noticeably improve image sharpness for individuals who have lost their sight due to retinitis pigmentosa, according to a study from the USC Roski Eye Institute and USC Viterbi School of Engineering.

What Is Retinitis Pigmentosa (RP)?

Affecting more than 1.5 million people worldwide, RP is a group of inherited retinal degenerative diseases that can lead to blindness and is characterized by loss of the light sensing cells known as photoreceptors.

What is Argus II?

Often referred to as the bionic eye, Argus II is the world’s first FDA- approved retinal prosthesis to give people who are otherwise blinded by RP the ability to see light.

 Graphical representation of the Argus II retinal prosthesis system
Graphical representation of the Argus II retinal prosthesis system

How Does Argus II Work?

The ophthalmic device consists of an eyeglass-mounted camera that transforms images from the camera into wirelessly transmitted electronic signals, while a 60-electrode retinal stimulator relays these signals to the retina via small electrical impulses. Signals are passed to the brain via the optic nerve and processed into a visual picture.

What Can Patients See with the Device?

Argus II retinal implants have provided an unprecedented degree of sight and have enabled blind individuals to detect motion and locate large objects. However, because the implants may unintentionally stimulate axons in the retina, patients sometimes see large oblong shapes of light that reduce the quality of their vision.

How Can Patients See More Clearly?

Mark Humayun, MD, PhD, James Weiland, PhD and Andrew Weitz, PhD, along with other USC researchers, found that axon stimulation can be avoided by increasing the duration of electrical impulses by a factor of 50. This allows visualization of distinct focal spots of light needed for patients with retinal implants to see more clearly.

“This is a huge step forward in helping restore sight to people with retinitis pigmentosa. Being able to create focused spots of light is important. Think of each light spot as a pixel in an image. By arranging many light spots into the shape of an object, we can generate sharp images of that object. For people with retinal implants, being able to see more clearly has a big impact on their ability to recognize objects and navigate their environments.”

—Andrew Weitz, PhD, Assistant Professor of Research, USC Roski Eye Institute