When Kim Norris began bumping into things, misjudging distances and walking past people she knew without realising, she assumed the problem lay with her new glasses.

But when she went to the optician, they assured her the prescription was spot on.

The problems worsened until, in 2021, doctors finally gave a diagnosis: the customer services agent from Warwickshire, 62, had a rare form of dementia.

It was posterior cortical atrophy (PCA) – a degenerative and ultimately fatal form of dementia that tends to strike earlier than most and begins by affecting the back part of the brain that processes visual information.

Explaining the condition, Kim’s husband Andy, 66, a retired car sales manager, says: ‘Her eyesight is fine – there’s nothing wrong with her eyes – but her ‘brain-sight’, the part of her brain that makes sense of what she sees, is scrambled.’

As part of Alzheimer’s Society’s Dementia Action Week, Andy revealed how PCA has turned Kim from an outdoors-loving woman into a prisoner in her own home.

And experts warn that while memory loss and language difficulties are the most common early signs of dementia, problems with vision can also be red flags.

Sebastian Crutch, Professor of Neuropsychology at University College London’s Dementia Research Centre, says: ‘Patients and healthcare professionals need to understand that dementia symptoms aren’t always what they expect.

Kim’s husband Andy explains: ‘Her eyesight is fine14745497 Kim started forgetting faces and bumping into things. She blamed her glasses – then doctors revealed she had dementia. Now they warn of the early sign too many ignore but her “brain-sight”, the part of her brain that makes sense of what she sees, is scrambled.’

‘With PCA, the early signs often relate to vision – such as struggling with visually or spatially complex tasks, for example parallel parking. People also report problems with reading, such as losing their place on the page or skipping words without noticing. Some even describe objects seeming to vanish before their eyes.’

Despite the alarming symptoms, diagnosis can take years. Prof Crutch adds: ‘The average age of onset for PCA is 59. But a triple whammy of factors can delay diagnosis. Firstly, symptoms don’t seem typical for dementia, because people aren’t complaining about memory problems.

‘Secondly, patients describe vision difficulties, so everyone assumes the problem is the eyes.

‘And thirdly, the misconception that dementia is confined to older people means doctors often think,’You’re too young for dementia… it must be something else.’ ‘

Dementia, which affects more than 980,000 people in the UK – is an umbrella term for illnesses causing a decline in brain function.

The most common form is Alzheimer’s, where it is thought that abnormal proteins build up in and around brain cells, typically in the middle part responsible for memory and language, causing confusion and speech difficulties.

However, PCA, a form of Alzheimer’s that is thought to affect five to 15 per cent of people with the disease, impacts where visual information is processed.

Patients struggle to recognise faces, perceive objects, or judge size and distance.

Most don’t initially suffer from memory loss or brain fog, but as the disease progresses it can spread across the brain, causing these typical Alzheimer’s symptoms. Declining brain function eventually leads to life-threatening complications, such as infections, dehydration and malnutrition.

Kim’s symptoms first emerged in 2019. Andy says: ‘When she went to the opticians, they were adamant she had the right lenses.’

An MRI showed no issues with her eyes or optic nerve, but after struggling in cognitive tests doctors said she had PCA.

Andy says: ‘We never imagined that Kim might have dementia.’

Throughout their 19-year marriage, the couple, who have adult children from previous relationships, enjoyed walking and sightseeing on holidays to Tenerife and Wales.

But PCA has left Kim, now 66, almost housebound.

Andy adds: ‘She points to something in completely the wrong direction. If there’s a black mat on a white floor she can’t tell if it’s a hole she could fall into.

‘She gets very confused, struggles with names and finds TV shows difficult to follow. Sudden noises make her jump. She puts her blouse on inside-out and her shoes on the wrong feet.’

Doctors estimate the life expectancy for a PCA patient is seven to eight years from diagnosis.

Andy says: ‘Kim’s aware of what’s happening and tries to laugh it off, but sometimes I find her sobbing. We agreed to maintain a sense of humour, but that’s getting more difficult with every passing day.’

In 2007, Sir Terry Pratchett – author of the Discworld fantasy novels who died in 2015 – was diagnosed with PCA at 59, and wrote: ‘It was my typing and spelling that convinced me the diagnosis was right. They had gone haywire.’

He added: ‘The disease slips you away a little bit at a time and lets you watch it happen.’

He had visited a support group run by Prof Crutch in partnership with Alzheimer’s Society, called Rare Dementia Support.

Prof Crutch says: ‘Most people have never heard of PCA. So when people are diagnosed, part of the fear is feeling that they’re the only one. That can be countered by meeting and sharing experiences with others who are living with this condition.’