The condition is often described as a visual variant of Alzheimer’s, giving rise to the following symptoms:

Blurred vision
Difficulties reading (particularly following the lines of text while reading) and writing.

According to Dr Marianne Chapleau, a neurologist from the University of California’s Department of Neurology, allocating greater resources to diagnosing PCA could change the quality of life for many patients who are in the primary stages of developing Alzheimer’s.

She said: “Most patients see their optometrist when they start experiencing visual symptoms and may be referred to an ophthalmologist who may also fail to recognise PCA. We need better tools in clinical settings to identify these patients early on and get them treatment.”

PCA holds particular promise for diagnosing dementia early because the signs of PCA surface before the age of 60.

Crucially, this is usually before the first signs of memory loss and confusion show up in those developing Alzheimer’s.

Writing in her research paper, Dr Chapleau’s notes that people with PCA first visit a doctor on average three years after symptoms appear.

By this time, mild or moderate symptoms dementia can be clearly seen, Dr Chapleau says.

PCA sufferers often present signs of what’s known as “constructional dyspraxia, space perception deficit, and simultanagnosia” when they were diagnosed, an inability to copy a drawing or build a simple model, researchers say.