Visual Perception Changes May Be an Early Warning Sign of Alzheimer’s Disease
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Memory loss may not always be the first noticeable symptom of Alzheimer’s disease. A new study suggests that some people, especially women, may experience changes in visual perception abilities even while their cognitive abilities seem normal.
To figure this out, researchers examined data on almost 1,100 people who had what’s known as posterior cortical atrophy (PCA), a condition which involves shrunken tissue in brain regions that play a role in interpreting and reacting to visual information. In day-to-day life, this can translate to problems with depth perception while driving or trouble reading, especially at night.
Autopsies revealed that 94 percent of these individuals had signs of Alzheimer’s disease, according to study results published in the Lancet Neurology journal — meaning PCA is almost always caused by Alzheimer’s.
PCA is diagnosed on average at age 59 — five or six years earlier than the average Alzeimer’s diagnosis, according to the National Institutes of Health. It is more prevalent in women, who account for 60 percent of cases.
While most people with PCA may initially have normal cognitive function, it can take around four years for them to get diagnosed, by which time they often have mild to moderate dementia, including deficits in memory, executive function, behavior, and speech, the study found.
But many people may not realize they have PCA or that it can be an early warning sign of Alzheimer’s disease, says lead study author Marianne Chapleau, PhD, a neuropsychologist and postdoctoral fellow in neurology at the University of California in San Francisco.
“Visual symptoms in PCA may precede noticeable and broader cognitive issues associated with Alzheimer’s, because individuals often attribute visual problems to aging eyesight rather than connecting them to dementia,” Dr. Chapleau says. As a result, they miss out on an opportunity for earlier intervention.
Visual Perception Problems
In the study, 61 percent of participants had so-called “constructional dyspraxia,” or an inability to copy simple diagrams or figures, at the time of their PCA diagnosis. In addition, roughly half of them had trouble identifying the locations of things they saw, as well as challenges perceiving more than one object at a time.
It’s not surprising that people might not immediately think of Alzheimer’s when they experience these symptoms, says Andrew Budson, MD, chief of cognitive behavioral neurology at VA Boston, a neurology professor at Boston University, and coauthor of Six Steps to Managing Alzheimer’s Disease and Dementia.
“They usually begin by going to their optometrist to get their eyeglasses prescription adjusted, then they might go to the ophthalmologist when the optometrist cannot help them,” says Dr. Budson, who wasn’t involved in the new study. “Only then will the ophthalmologist realize that the problem is likely in the brain and not related to the eyes and refer the patient to a neurologist.”
But even that initial neurology consultation might not lead to a PCA diagnosis, Budson says. People might still need a magnetic resonance imaging scan (MRI) showing brain shrinkage patterns consistent with PCA, followed by a consultation with an expert in dementia or memory disorders.
Benefits of an Earlier Diagnosis
Getting a PCA diagnosis as soon as possible is crucial because there are steps people can take to manage symptoms, Budson says. Because PCA is typically caused by Alzheimer’s, treatment with what’s known as anti-amyloid medicines like lecanemab (Leqembi) may slow symptom progression.
While more research is needed, it might one day be possible to detect PCA at its earliest stages and prevent it from getting worse with these Alzheimer’s drugs, Budson says.
While there’s no specific way to avoid developing PCA or cure the condition, lifestyle changes can still yield benefits, Chapleau says.
“Adopting a healthy lifestyle with regular exercise, a balanced diet, and cognitive activities may contribute to overall brain health,” Chapleau says. “Once diagnosed, managing symptoms and slowing the progression of dementia can be supported through interventions like cognitive therapies, medications, and individualized care plans.”
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