Quantum Physics Could Someday Power A New Eye Test

Scientists Made a Faint Eye Pattern Bloom Into Six Petals

Quantum physics gave the world GPS navigation, MRI scanners, and computer chips. Now a technique from the same field is being pointed at something far smaller: a faint, bowtie-shaped smudge that can appear at the edge of vision under the right kind of light. Researchers used engineered light to stretch that bowtie into a glowing, six-lobed flower, and they hope the effect could someday lead to a noninvasive way to check the health of the retina, the light-sensing tissue at the back of the eye.

Called Boehm’s brushes, the bowtie has been known since 1940, and scientists have long wondered whether it could act as a biomarker, a measurable sign of retinal health. Unlike the better-known Haidinger’s brushes, an hourglass shape at the center of vision, Boehm’s brushes show up off to the side. Visibility is the sticking point. Ordinary versions are often too faint to be useful, even for people with healthy eyes. The new technique, the researchers say, makes the pattern easier to see.

A team from the University at Buffalo and the University of Waterloo’s School of Optometry, along with Hong Kong’s Centre for Eye and Vision Research, reported the results in the Proceedings of the National Academy of Sciences.

Structured Light Expands a Faint Bowtie Into Six Petal-Like Lobes

Polarized light, which vibrates in a single direction instead of every direction at once, is thought to bounce off tiny structures in the retina’s inner layers and produce that bowtie. Ordinary polarized light yields only the two-lobed version. Structured light, a beam whose polarization has been deliberately arranged in a pattern across its width, produced a many-lobed pattern. Where the beam’s polarization directions point toward a common spot, the paper explains, the faint signals from the retina add together, making brighter, sharper lobes.

Two white light sources, one passing through a spinning polarizer, were blended to control how much of the beam was polarized. The light then went through ring-shaped openings and a liquid crystal plate that arranged its polarization in a twisting pattern. A green filter picked the color, and a lens focused the ring onto each volunteer’s retina while they stared at a small dot in the middle. Rings of six sizes covered a narrow zone from roughly half a degree to four degrees, measured as an angle away from where the eyes are aimed. Retinal photographs of each volunteer calibrated those angles. Only the right eye was tested.

In the researchers’ math, the number of lobes follows from how the beam’s polarization twists around the ring. Simulations in the paper show anything from two to six lobes, some sprouting outside the ring and some inside its dark center. Volunteer testing, though, centered on the six-lobed version, so the rest of that lineup rests on the model, not on human testing.

Each volunteer watched the glow for a quarter of a second and said whether it seemed to rotate clockwise or counterclockwise. After two correct answers in a row, the system weakened the polarized signal, and after a mistake, strengthened it, homing in on the faintest version each person could still detect.

Sixteen people signed up, all recruited at the University of Waterloo and screened with vision tests and retinal scans. Eleven completed everything. One dropped out, one proved ineligible, two hit technical snags with retinal imaging, and one felt discomfort and showed no measurable sensitivity to the pattern at all. Volunteers were paid, and the paper’s main text does not give their ages or sex.

Structured Light Patterns Became Easier to Detect Away From Center

Near the center of gaze, the beam had to be strongly polarized before anyone noticed it rotating. By four degrees out, a much fainter version registered. By the researchers’ estimate, volunteers at about one degree off center needed, on average, roughly half the beam to be polarized, with the rest ordinary light. All eleven showed the same overall trend, even though some were more sensitive than others, a difference the authors attribute to possible variation in retinal anatomy. This trend matches measurements of ordinary Boehm’s brushes from 1964, which also found weak sensitivity near the center.

Eye Disease Detection With Structured Light Remains Unproven

Corresponding author Dusan Sarenac of the University at Buffalo said the added lobes offer “multiple ways to measure patients’ perception of the phenomenon.” Damaged retinal tissue might scatter light differently and change what a person sees. In glaucoma, for instance, early loss of nerve fibers near the retina’s center could alter the pattern, and the paper also names macular degeneration, an age-related condition that damages central vision, along with diabetes-related retinal damage as candidates for study.

That is still a hypothesis. Nobody with retinal disease took part, and the researchers acknowledge that no rigorous model yet explains how retinal scattering produces the patterns people see. Sarenac said the next step is testing people with retinal disease.

For now, the glowing flower at the edge of vision is a clever lab result, not an eye exam.

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Disclaimer: This article is for general information only and is not medical advice. The study described was an early laboratory experiment in healthy volunteers, and it does not show that structured light can detect or diagnose eye disease. Anyone with concerns about their vision or eye health should consult a qualified eye care professional.

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