A study conducted by the University of South Australia has gone against the common literature relating poor eyesight to brain decline, finding that cognitive tests can misdiagnose older people with age-related vision decline with cognitive decline by up to 25 percent.
The research team recruited 24 participants with normal vision to do cognitive tests—one that is vision dependent and tests reaction time and another on verbal fluency. They then fitted the participants with a pair of goggles to simulate AMD.
They found that under AMD conditions, the reaction time scores dropped from the 50th percentile to the lower 25th percentile, though verbal fluency scores remained stable under both conditions.
“Being scored in the 25th percentile instead of the 50th percentile,” the authors wrote, “is a significant reminder to researchers that the added interference due to vision loss deserves attention and should not be easily discounted.”
The authors noted that the results are a reminder for researchers, especially neuro-degenerative researchers, to control for vision when assessing patients’ cognition, as mistaken scores may bring negative consequences of “psychological problems including depression and anxiety,” Macnamara 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,” she said.
“While the true impact of AMD on cognitive test scores remains to be established, it is clear that not controlling for vision can adversely affect the results and can have broader implications for the health of visually impaired people,” the authors concluded.