Everyone knows the phrase “seeing double,” but only those who have experienced it know the frustration and disruption caused by the condition. They also know the difficulty of correcting it — as do their ophthalmologists.

“One of the challenges of double vision — particularly that caused by neurological conditions as opposed to corneal ones — is that a person’s double vision can change depending on the direction in which they look,” says Andrew Carey, M.D., assistant professor of ophthalmology and neurology in the Neuro-Ophthalmology Division of Wilmer Eye Institute, Johns Hopkins Medicine.

Patients often categorize their double vision as horizontal or vertical depending on where they see the second image. The essential question for treatment, however, is not just where the second image is but also how far apart the two images are and if that distance changes as a person’s head moves. “If the distance between the two images is the same in every direction, that’s called comitant. And if it changes depending on the direction of where they’re looking, it’s called incomitant,” says Carey.

Incomitant double vision is the most difficult to correct. “Because of the optical limitations of the prisms used to treat double vision, ophthalmologists can try to make it so that you see a single image when you look straight ahead, but if you look to the side, you’re probably still going to see double again,” says Amanda Henderson, M.D., associate professor of ophthalmology and neurology and chief of the Neuro-Ophthalmology Division.

This is the current state of play — but a potential solution is in the works. Last year, Chad Weiler, Ph.D., a research optical physicist, and David Shrekenhamer, Ph.D., a metasurface scientist, of the Johns Hopkins University Applied Physics Laboratory, approached Wilmer’s Neuro-Ophthalmology Division with a nanotechnology called a metasurface optic with which they are experimenting. They wanted to know if it could be useful outside of a lab. When they explained what it could do, Carey and Henderson grew excited about the possibilities.

“The idea is that rather than having one lens that can have one particular correction built in, they can vary the correction throughout the entire lens. In theory, you could have any sort of gradient that you want in any direction,” says Henderson. Such a lens could give a patient a wider field of view in which they would not see double.

“This would improve their ability to function in everyday life and their safety. They would be able to walk around and not worry about tripping over things because they’ve lost their depth perception when looking down, for example,” says Carey.

Metasurface optics are made of subwavelength scatterers, “which can be thought of like nanoscale antenna-like structures that scatter light in ways dictated by their arrangement,” says Weiler. Nanoscale refers to a size measured in nanometers. As a reference, a human hair is approximately 80,000-100,000 nanometers wide.

For this application, the subwavelength scatterers would be optically transparent. Picture a (transparent) flexible brush with plastic bristles that can be arranged in any pattern. The arrangement of the “bristles” and whether the back of the “brush” is flat or curved allow the optical physicist to manipulate how the light moves through the structure “in extremely customizable ways,” says Weiler.

This is in comparison to how prism lenses — the current treatment for double vision — work, which involves refraction, or manipulating how light bends through a surface. Metasurfaces provide a unique way to manipulate the movement of light, which allows for more customizable control. “That ability should allow optical physicists to customize the creation of lenses to a level of individuality previously impossible,” says Weiler.

The team has created proof-of-concept designs for other application spaces, and is now looking to transition to vision-specific technologies. They are casting a wide net to fund these efforts.

Despite the challenge to secure funding in a competitive environment, their enthusiasm is high and motivation powerful.

“Seeing the smile on someone’s face after their quality of life has been changed by the technology you have developed is an extremely rewarding feeling,” says Weiler. “The collaborative spirit developed with the skilled clinicians at Wilmer has opened an opportunity for solving continued challenges clinicians identify as the next advances for health care.”

“There are very few places in the world where you get these kinds of opportunities. It’s the real value of being at Wilmer, and it’s a privilege,” says Carey.

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