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Supporting a person with dementia who’s experiencing vision and perception problems

Ways to approach helping a person with dementia who is mistaking what they’re seeing for something else.


‘My wife’s dementia sometimes makes her mistake what she’s seeing and misjudge distances. How can I find ways to help her?’


As a person’s dementia develops, they may experience changes in their vision and in how they understand what they see. 

This can include misperceptions – seeing one thing as something else, such as a dark rug for a hole in the floor. It could also involve misidentifications – incorrectly identifying people or objects, such as mistaking a spouse for a sibling. 

Things to rule out 

Sometimes mistakes are caused by sight problems. An optician can see if your wife needs glasses or if there’s something else affecting her sight. 

If your wife already wears glasses or contact lenses, the optician can make sure they’re the correct prescription.

Are her glasses scratched or dirty? If your wife has a pair for a specific activity, such as reading, are they labelled or marked clearly? 

You should also ask your wife about what she’s seeing to check if she’s experiencing hallucinations – seeing things that aren’t actually there. 

Hallucinations can be confusing and distressing, and hallucinated images could get in the way of seeing real objects and judging distances. If you think your wife is experiencing them, speak to her GP.

Patterns or triggers 

If you’ve ruled out sight problems and hallucinations, then a general problem-solving approach can help with misperceptions and misidentifications. 

Think about what your wife experiences around the time she has these problems.

You can sometimes find patterns or triggers, which you might be able to remove or minimise. A starting point would be to make a note of when problems occur. 

For example, if problems usually happen toward nighttime, they might be caused by ‘sundowning’ (changes in behaviour that usually happen toward the end of the day) or because there isn’t enough light. Dealing with the sundowning or increasing the lighting could prevent or reduce the problems. 

Difficulties that only happen when lights are switched on might be caused by shadows or certain types of lighting. Spotlights or other harsh lighting can cause problems by making corners of a room look darker than usual. 

If your wife misidentifies a particular person, it could help for that person to introduce themselves when they see her.

If you’re handing something to her, clearly letting her know what it is could help her to identify it. If she misjudges distance when reaching for an object, place it before her on a table or in her lap while saying what it is. 

Supporting the person 

If you can’t identify any triggers, then focus on supporting your wife to manage how it feels when these problems occur, and any changes you could make around the home to help her. 

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If you or someone you know are worried about or affected by dementia, we are here for you. Get advice on a range of topics and find support near you.

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I am the wife of a man that is not the same person and displaying for over 3 years now symptoms off dementia. He has gone thru an MRI and EEG, both test came back negative for dementia only aging process they say. I worked with Alzheimer’s patients and definitely recognize some of the same symptoms, I have watched my husband display many symptoms over the last few years. Right now we are about to go to the 3rd opthymologist,and they find no changes in his vision, which is very bad. His perception is off, and he has started with misconceptions such as seeing water over the road when there’s nothing there.He now walks into the same room I Amin and can’t get me our our dog into his vision. I need help with this.he is a veteran and the Dr. There gave him a simple test of remembering and he did fine, so they say mo dementia….Now after that experience, we saw a neurologist whom ordered the MR I and EE G. Nothing much shows up they said..Thanks for letting me go on and on,

Hello Rita,

Thanks for your comment. Please know that if you ever need someone to speak to, we are here for you. You can always call our support line on 0333 150 3456, where you can speak with one of our trained dementia advisers. They are there to listen to you and provide support and advice specific to your situation. You can find more details about the support line (including opening hours) here: https://www.alzheimers.org.uk/dementia-connect-support-line 

You might also benefit from joining our online community, Talking Point, where people affected by dementia share their experiences, and offer advice and support to people who may be going through similar situations. You can explore the community or sign up for free here: https://www.alzheimers.org.uk/get-support/dementia-talking-point-our-online-community

Wishing you all the best, Rita.

Alzheimer's Society blog team

My father suffered with glaucoma-needing eye drops to maintain a less dangerous pressure in his eyes, (but these cannot remove damage to the optic nerve that may already have occurred). That meant he often misjudged distance or position , for example not able to put a key in the keyhole or his cuppa back on the table easily. For different reasons things got very difficult at times when he was becoming delirious as he was seeing all manner of hallucinations but I did not realise just what was happening when this first started . We began to understand how dangerous a state of delirium was after help from a community psychiatric worker- the GP service seemed only able to check for symptoms that could suggest why delirium and hallucinations were occurring , ( like constipation or a urine infection), but then not able to address the delirium . It took me a while to realise therefore that hallucinations might be the signal that delirium was happening and that this represented a medical emergency . Eventually my father could see that talking about what might be hallucinations was helpful , even if after the event or episode . He was hospitalised 4 times over the course of 3 years because of delirium and the dangers this represented, it was very traumatic for him and for me. Lewy body disease/dementia seems to increase the likelihood of hallucinations.

Thankyou for this. My farther us hospital after a fall, they have said he has delirium, we see his issues triggered by by heat, dehydration, water infection, but the 'health system' just seems to want to push him around each suggesting he needs to be cared for elsewhere. We know his triggers we just need help managing them to reduce the chance of escalation but it is convincing doctors etc. that we know our dad and how he works!!
Nigel -hoping the delirium is starting to reduce slowly , it will be awful for you with the heat and impossible strains on health service. I would spend a lot of energy explaining to the ever-changing list of health professionals what my father was normally like (not raving at a window because there was someone with a gun ), but able to walk into his garden and sow some seeds for veg to eat (not excavating the end of the bed as there were snakes crawling up his legs), and able to cook some food rather than needing to be spoon-fed, and so on. I would spend as much time in hospital with my father as was possible (pre-covid) in order to help him eat , drink , listen to familiar music and try to prevent other equally disturbed patients from upsetting him further. One time I did manage to care for him at home during 10 days delirium but with daily support from a "Dementia Rapid Response unit" which I did not even know existed-all so joined up. That in itself had its dangers as I had to go out to get more anti-psychotics and my father deceided to go and water the garden and fell , more damage to the runner beans then himself thankfully ,but could not then get up.