One aspect of thinking affected by dementia is sensory perception.
This means that a person with dementia might have good eyesight (or corrected with glasses), but their brain may have difficulty converting the signals from their eyes into a meaningful picture. They might experience trouble with depth perception, like judging how deep or far away something is may be difficult. They may also struggle to pick out an object from its background, particularly if it’s the same colour as the background, there are shadows, or the background is patterned.
For instance, Erik used to set out Mary’s clothes for the day on the bed, and Mary would often get angry saying
it isn’t helpful when there is no underwear!”
Exasperated, Erik would then say,
it’s there right in front of you”.
An occupational therapist later pointed out that Mary had difficulty seeing white clothes against the white bedsheet. Placing the clothes on a contrasting bedspread solved this issue.
People with dementia may also have difficulty interpreting visual information when there is a mirror, or reflections from wet or shiny surfaces, or a glare.
Sara found walking on the swirly patterned carpet at the library almost impossible and needed an arm to steady her.
Perceptual changes may also affect the way people with dementia experience hearing, touch, smell, and taste.