Strong association between vision loss and cognitive decline

Photo by Les Black

In a nationally representative sample of older adults in the United States, Stanford researchers found a strong relationship between visual impairment and cognitive decline, as recently reported in JAMA Ophthalmology.

The research team investigated this association in elderly populations by analyzing two large US population data sets — over 30,000 respondents from the National Health and Aging Trends Study (NHATS) and almost 3,000 respondents from the National Health and Nutrition Examination Study (NHANES) — which both included measurements of cognitive and vision function.

“After adjusting for hearing impairment, physical limitations, patient demographics, socioeconomic status and other clinical comorbidities, we found an over two-fold increase in odds of cognitive impairment among patients with poor vision,” said Suzann Pershing, MD, assistant professor of ophthalmology at Stanford and chief of ophthalmology for the VA Palo Alto Health Care System. “These results are highly relevant to an aging US population.”

Previous studies have shown that vision impairment and dementia are conditions of aging, and their prevalence is increasing as our populations become older. However, the Stanford authors noted that their results are purely observational and do not establish a causative relationship.

The complexity of the relationship between vision and cognition was discussed in a related commentary by Jennifer Evans, PhD, an assistant professor of epidemiology at the London School of Hygiene and Tropical Medicine. She stated that this association could arise owing to problems with measuring vision and cognitive impairment tests in this population. “People with vision impairment may find it more difficult to complete the cognitive impairment tests and … people with cognitive impairment may struggle with visual acuity tests,” she wrote.

Assuming the association between vision and cognitive impairment holds, Evans also raised questions relevant patient care, such as: Which impairment developed first? Would successful intervention for visual impairment reduce the risk of cognitive impairment? Is sensory impairment an early marker of decline?

Pershing said she plans to follow up on the study:

“I am drawn to better understand the interplay between neurosensory vision, hearing impairment and cognitive function, since these are likely synergistic and bidirectional in their detrimental effects. For instance, vision impairment may accelerate cognitive decline and cognitive decline may lead to worsening ability to perform visual tasks. Ultimately, we can aim to better identify impairment and deliver treatments to optimize all components of patients’ health.”

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Researchers Have Vision-Correcting Computer Screens In Their Sights

eyeglasses resting on laptop
Eyeglasses may no longer be necessary to see computer screens. (F H Mira, flickr)

What if everyone could clearly see their smart phone, tablet, computer and TV screens without having to wear corrective eyeglasses or contact lenses?

Approximately 75% of American adults use some form of corrective lenses to see or read properly. And most of us need them to see computer screens on a daily basis. Now researchers are developing new technology that uses computer algorithms to compensate for an individual’s visual impairment, so many of us may soon be able to ditch our glasses and contacts.

Brian Barsky, UC Berkeley professor of computer science and vision science and affiliate professor of optometry, teamed up with colleagues at UC Berkeley and MIT to improve vision-correcting display technology. They developed a combination of hardware and software improvements to achieve both high image resolution and contrast simultaneously, a major milestone. Their results were recently published in a paper in the ACM Transactions on Graphics.

First, they modified an iPod touchscreen by adding a standard light field display – a mask with an array of pinholes sandwiched between thin layers of plastic. The tiny pinholes were each 75 micrometers in diameter and spaced 390 micrometers apart. This light field display was used to enhance image contrast, providing a full range of bright colors in the displayed images.

The researchers also developed complex, innovative computer algorithms to adjust the light intensity from each pinhole. These algorithms helped enhance the resolution or sharpness of the displayed images. The researchers can use a person’s eyeglass prescription to compute an altered image, that when viewed through the light field display, appears in sharp focus for that individual.

“Our technique distorts the image such that, when the intended user looks at the screen, the image will appear sharp to that particular viewer,” said Barsky in a press release. “But if someone else were to look at the image, it would look bad.”

The technology could not only help the millions of people who wear glasses and contacts, but also those with complex vision problems that cannot be corrected. The most common vision problems – nearsightedness, farsightedness and astigmatism – are usually easily corrected with standard lenses. However, people with complex vision problems often have irregularities in the shape of their eyes’ surface or cornea, requiring new kinds of corrective lenses that are still under development.

“We now live in a world where displays are ubiquitous, and being able to interact with displays is taken for granted,” said Barsky. “People who are unable to view displays are at a disadvantage in the workplace and life in general, so this research could transform their lives.”

In the future, the researchers plan to incorporate commercially available eye trackers to adapt the displayed images to the user’s head position. They also hope to develop display screens that appear clear to multiple users with different visual problems.

This is a repost of my KQED Science blog.