A new clue for aging eyes

Struggling to read more than six lines on an eye chart with fading letters may serve as a visual “yellow light” for older adults—raising red flags that routine exams sometimes fail to detect. A new University of Michigan study, published in JAMA Ophthalmology, shows that this threshold on a Pelli-Robson chart might indicate everyday vision problems that standard eye tests may miss.

“Traditional eye charts can miss important vision changes that often occur as we age because they use high contrast with black letters on a white background,” said U-M neuro-ophthalmologist Lindsey De Lott. “But we can also measure vision using letters in different shades of gray. In these lower-contrast charts, such as the one used in our study, the letters become progressively lighter and harder to see. We call this contrast sensitivity.”

Researchers have long known that contrast sensitivity is a better way to detect certain vision problems, according to De Lott. “But we didn’t have a threshold or number that told us where on this contrast sensitivity chart patients start to experience problems with their vision in their day-to-day lives, like trouble recognizing faces, reading print or watching television,” she said.

According to the researchers, before this study, the yellow light was defined based only on patients reporting no visual problems. Now, doctors might be able to help them before they reach the red light.

“This makes the test more actionable for clinicians and more meaningful for patients,” said Shu Xu, a postdoctoral fellow at U-M’s Institute for Social Research. “It also provides researchers in public health, aging and the social sciences with a concrete marker for studying how vision affects older adults’ independence, well-being and health outcomes.”

Many older adults with normal visual acuity scores still had poor contrast sensitivity and reported vision problems, highlighting a gap in routine care. Traditional vision testing may miss important aspects of visual function that affect daily life.

A hard-to-diagnose problem

Many older adults report that their vision is not as reliable as it used to be. Some struggle to navigate uneven sidewalks at dusk, while others have difficulty reading medication labels in dim light or seeing objects that do not stand out clearly from their backgrounds.

Contrast sensitivity is the ability to detect subtle differences between a target and its background. Poor contrast sensitivity has been linked to important real-world outcomes, including falls, difficulty driving and loss of independence.

“Clinicians and researchers often label scores two standard deviations below the mean as impaired, which simply tells you that you are worse than average—not that you are likely to have trouble in real life,” Xu said. “Our work provides that missing link by connecting the test result to older adults’ real-world daily experiences.”

According to the researchers, this is the first study to link contrast sensitivity directly to older adults’ self-reported visual difficulties in daily life. They used data from 4,475 Medicare beneficiaries in the National Health and Aging Trends Study, making the results nationally representative. Previous studies often relied on small clinic samples or statistical cutoffs that were not tied to people’s everyday experiences.

“Our functional anchoring makes the threshold more relevant for clinical decision-making and public health,” De Lott said. “We found that people began reporting trouble even when their vision measured using traditional charts would not be considered impaired. This means real-world difficulties may emerge earlier than previously recognized.”

What the findings mean for care

Adults 65 and older who report poor vision despite normal exam results may benefit from contrast sensitivity testing. Early changes in vision can appear before standard visual acuity declines, and several causes can be treated.

“We are currently building on this work by examining whether older adults with contrast sensitivity below the newly identified threshold are at greater risk of future declines in health and independence,” Xu said. “By following people over time, we hope to better understand how this functionally meaningful threshold can help identify older adults at risk for functional decline and support healthier aging.”

Who’s behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

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Andrew Zinin

Master’s in physics with research experience. Long-time science news enthusiast. Plays key role in Science X’s editorial success.

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