Poor eyesight linked to ‘devastating’ cognitive misdiagnosis

New research has found that older people with poor eyesight might be mistakenly diagnosed with cognitive impairment.

Age-related macular degeneration (AMD) affects one in seven people over the age of 50 and is the leading cause of blindness.

During cognitive assessments, visual impairments such as AMD are overlooked in almost half the clinical cases.

Researchers from the University of South Australia aimed to find out how significant the influence of poor eyesight was on cognitive test results.

Twenty-four participants underwent two cognitive tests. In one test they wore goggles that blurred their vision.

“We found that when we simulated vision loss, there was a significant negative effect on the vision-dependent test scores, but not the vision-independent test scores,” lead author Sarah Anne MacNamara said.

“​​So when vision is critical to the context of a test, it is possible that the results of visually-impaired people may not accurately reflect their cognition.”

MacNamara said that false test results pointing to mild cognitive impairment can trigger psychological problems, such as anxiety and depression.

“A mistaken score in cognitive tests could have devastating ramifications, leading to unnecessary changes to a person’s living, working, financial or social circumstances,” she said.

“People with AMD are already experiencing multiple issues due to vision loss and an inaccurate cognitive assessment is an additional burden they don’t need.”

AMD has a serious impact on a person's day-to-day life, rendering tasks such as reading, driving and cooking more difficult.

People may initially associate blurry vision as a natural result of ageing, which could leave serious medical conditions left undiagnosed, MacNamara said.

“AMD and other visual impairments often start with mild visual loss, but it’s progressive and degenerative.

“Because it's slowly over time, you may not notice immediately that your eyesight is getting worse.”

As people age, the risk of developing a neurodegenerative disease, such as dementia, significantly increases.

Cognitive screening and assessments are vital to detect early signs, but often rely on visual and auditory performance for results.

“There are a lot of paper-and-pencil type cognitive assessments, where there's material that you are looking at, and you need to write or respond or draw something, which would be particularly affected by poor vision,” MacNamara explained.

“Whereas, some of the vision independent cognitive assessments can be more verbal, which is not reliant on your sight: therefore that would be less affected.”

Unreliable test results due to poor eyesight can be prevented by performing prescreens and using mobile apps.

“Doing a quick test on visual acuity would give the researcher a sense of whether the participant has an appropriate level of vision to complete the test,” MacNamara said.

“Mobile apps can also now be used to overlay simulated visual impairments onto test materials when piloting their stimuli.

“Alternatively, researchers could balance the visual aspects of the test that do not require vision, which is the verbal auditory assessments.”

MacNamara said she hopes this research mobilises the scientific community to consider effective vision in assessing cognitive functioning.

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