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A new study shows about 94% of people with a rare vision condition known as posterior cortical atrophy also have Alzheimer’s. Cavan Images/Juan Ramón Ramos Rivero/Getty Images
  • Alzheimer’s disease affects the brain and may also have an impact on the eyes.
  • A new study reported about 94% of people with a rare vision condition also had Alzheimer’s pathology.
  • Scientists urged the need for more clinical awareness of the condition, known as Benson’s syndrome, to help detect Alzheimer’s earlier.

Researchers estimate that about 32 million people have a type of dementia called Alzheimer’s disease, with another 69 million at the prodromal stage, which is defined as having mild cognitive impairment.

It’s well understood that Alzheimer’s impacts brain functions such as memory, spatial awareness, speaking, and writing, but lesser known are the changes to the brain associated with the condition that may also impact the eyes.

Previous studies show that changes that occur in the brain with Alzheimer’s may also happen in the retina of the eye. Researchers have also noted eye changes with Alzheimer’s, including contrast sensitivity required for reading, color vision, and visual field loss.

In a new study, researchers from the University of California — San Francisco examined how Alzheimer’s affects the eye by identifying the effects of a rare eye condition known as posterior cortical atrophy or Benson’s syndrome.

Scientists reported that about 94% of people with posterior cortical atrophy also had Alzheimer’s disease pathology.

Based on their findings, researchers urged the need for more clinical awareness of posterior cortical atrophy for earlier diagnosis of Alzheimer’s disease.

The results were published in the journal The Lancet Neurology.

Posterior cortical atrophy — also known as Benson’s syndrome — is a rare neurodegenerative disorder affecting vision.

The disease causes brain cells to die in the back portion of the brain responsible for managing what a person sees.

“Posterior cortical atrophy is a progressive brain disorder that affects visual regions in the brain,” Dr. Gil Rabinovici, neurologist and director of the Alzheimer’s Disease Research Center at the University of California — San Francisco and senior author of this study, explained to Medical News Today.

“Over time, visual loss can progress to the point of functional blindness.”

The first symptoms of posterior cortical atrophy normally occur between the ages of 50 and 65. Symptoms can vary between individuals but normally include:

  • vision issues
  • difficulty recognizing people, places, and/or objects
  • reading difficulties with words and/or numbers
  • inability to judge distances correctly
  • bumping into doorways and furniture when moving
  • problems driving
  • unable to identify left from right
  • anxiety
  • confusion
  • behavioral changes

Although previous studies have found posterior cortical atrophy is most commonly associated with Alzheimer’s disease pathology, the prevalence of the condition is still unknown.

Researchers estimate that between 5–15% of people diagnosed with Alzheimer’s disease may also have posterior cortical atrophy.

“From a clinical point of view, posterior cortical atrophy is probably the second most common clinical presentation of Alzheimer’s disease after memory loss, yet it is under-recognized, and patients can go undiagnosed or misdiagnosed for years,” Dr. Rabinovici said.

“There has been a major need in the field for a large, international multi-site study that comprehensively characterizes the syndrome and raises awareness amongst clinicians.”

“Alzheimer’s disease is defined biologically by the presence of toxic proteins called plaques and tangles in the brain, causing brain dysfunction and brain tissue loss. In most patients, these proteins affect memory regions in the brain early on, but in posterior cortical atrophy, for reasons that we don’t really understand, these proteins accumulate early on in visual areas that are located in the back (posterior) parts of the brain.”

— Dr. Gil Rabinovici, neurologist

For this study, Dr. Rabinovici and his team analyzed data from more than 1,000 people with posterior cortical atrophy at 36 medical research centers in 16 countries.

The researchers found that about 94% of study participants with posterior cortical atrophy also had Alzheimer’s disease pathology, while the remaining 6% had other dementia conditions including Lewy body disease and frontotemporal lobar degeneration.

Scientists also reported at the time of participants’ diagnosis:

  • 61% had constructional dyspraxia (inability to build a simple structure with blocks or copy a drawing)
  • 49% had space perception deficit (problem with moving through an environment or properly gauging distance between themselves and an object)
  • 48% had simultanagnosia (inability to see more than one object at a time)
  • 47% had newly developed challenges with basic math calculations
  • 43% had new issues with reading

Dr. Rabinovici said their findings should encourage neurologists and eye care professionals to consider posterior cortical atrophy in people with slowly progressive visual loss not explained by primary eye disease.

“Early brain scans such as MRI can clarify that the problem is in the brain, not the eyes, since tissue loss in the visual areas of the brain can be profound,” he continued.

“Further tests like PET scans, spinal fluid, or blood tests for Alzheimer’s disease proteins can seal the diagnosis of posterior cortical atrophy due to Alzheimer’s disease.

And Dr. Rabinovici said that earlier identification of posterior cortical atrophy can allow people to access established treatments for Alzheimer’s, as well as new treatments like the antibodies that remove amyloid from the brain.

“These treatments are more effective the earlier in the disease course they are started,” he explained. “An early and accurate diagnosis can facilitate care planning for patients and their families.”

“Furthermore, patients can avoid unnecessary and unhelpful procedures such as constantly trying new eyeglasses or even undergoing surgery for early cataracts that are not actually the cause of vision loss,” Dr. Rabinovici added.

MNT also spoke with Dr. Alexander Solomon, a surgical neuro-ophthalmologist and strabismus surgeon at Pacific Neuroscience Institute in Santa Monica, CA, about this study.

Dr. Solomon commented that it is extremely useful to see such a large and thoroughly evaluated data set on the strong connection between Alzheimer’s and posterior cortical atrophy, but as a clinician who treats these patients, it is hardly surprising given the disease is sometimes known as the visual variant of Alzheimer’s.

“It is good to see more attention being brought to the disease, which I think (is) more awareness from neurologists than your average eye care professional. I think it can serve as an impetus to start screening patients complaining about difficulty with visual processing early for evidence of underlying posterior cortical atrophy by referring them appropriately to a neurologist, neuropsychologist, or neuro-ophthalmologist more familiar with diagnosing the condition.”

— Dr. Alexander Solomon, surgical neuro-ophthalmologist

Dr. Solomon said this study would be a good springboard to help develop prospective studies on how best to screen and diagnose patients presenting with some of the symptoms of posterior cortical atrophy to help achieve better and earlier diagnostic certainty and to see how many of these correlations hold up.

“(The researchers) alluded to the fact that one weakness here is that diagnosis was made by individual practitioners with varying diagnostic criteria with almost no limit to how long ago this diagnosis was made, and thoughts/attitudes/criteria have shifted over time which could affect results,” he explained.

“I’d also be really interested to see the efficacy of some of the clinical tests for Alzheimer’s as screening tools for the disease, as this may encourage more widespread and earlier use of these tests if appropriate.”