Perception and hallucinations

3. Visuoperceptual difficulties in people with dementia

The specific difficulties a person experiences will depend on the type of dementia they have. This is because each type of dementia can damage the visual system in a different way.

Difficulties may include:

  • being less sensitive to differences in contrast, such as black and white, and contrast between objects and background
  • being less able to detect movement
  • changes to the visual field (how much you can see around the edge of your vision, while looking straight ahead)
  • being less able to detect different colours. For example, a person may have problems telling the difference between blue and purple
  • changes to how the pupil reacts to light
  • problems directing or changing gaze
  • problems with the recognition of objects, faces and colours
  • losing the ability to say what has been seen
  • double vision
  • problems with depth perception (judging the distance of objects from the person).
  • Difficulties with orientation

Dementia can also cause difficulties with orientation. This can lead to:

  • bumping into things
  • swerving to avoid door frames
  • difficulties reaching for things , such as a cup of tea or door handle
  • getting lost or disorientated, even in familiar environments.

These difficulties can have a big impact on the person with dementia. They may include:

  • difficulties with activities and hobbies such as reading and writing
  • problems locating people or objects, even if they are in front of the person. This may be because of other visual distractions (such as patterned wallpaper) or because of a lack of contrast (for example, not seeing mashed potatoes on a white plate)
  • misinterpreting reflections such as seeing an ‘intruder’ or refusing to go into a bathroom because it looks as if someone is in there
  • mistaking images on the TV for real people
  • having difficulty positioning themselves on a chair or on the toilet
  • becoming confused or restless because the environment is visually over-stimulating (has ‘too much going on’) and is difficult to navigate. For example, a room with patterned wallpaper, bright lights or too many signs.

Difficulties with moving around

  • Visuoperceptual difficulties can also lead to problems moving around. Consequently, people with dementia may:
  • Misjudge distances and where objects are, even in familiar environments
  • Step too highly over carpet rods or shadows because the change in colour looks like a change in level or height
  • Have difficulty going down stairs due to problems judging how many steps there are and where the next one is
  • Try to avoid shiny floors and surfaces because they appear wet or slippery.
  • These problems can make a person afraid of falling and lead to them slowing down their movements while they try to walk safely.

Tips

Try to anticipate the situation and explain the environment. For example, if you notice someone avoiding a room with a shiny floor or surface, walk in first to show the person that it’s safe.

  • Offer the person plenty of support and encouragement.
  • Try not to make the person feel rushed, and allow them plenty of time.
  • Slow down your own movements.

If a person with dementia is living at home with other people, it may not be clear how their visual difficulties affect them until they experience a change in environment. This may include visiting family, going out shopping or going on holiday.