Monday, 19 May 2014

Visuoperceptual difficulties in dementia

After having around a year of eye tests, and now finding that things are no different, I started to look for more information, and today I found this sheet on the Alzheimer's Societies web site.

I now know that these problems are caused by the illness, and by copying this web page I hope it helps others
 

This factsheet considers some specific visuoperceptual difficulties that people with dementia can have,
and possible ways of helping them.

Understanding potential perceptual problems and intervening with
appropriate help, support and reassurance can greatly assist people with dementia to feel safe in their
changing perceived reality.

 People with dementia can experience a number of visuoperceptual difficulties due to normal ageing,
eye conditions, and sometimes from additional damage to the visual system caused by specific types
of dementia.

Vision difficulties can result in a variety of 'visual mistakes' (including illusions, misperceptions,
misidentifications and sometimes even hallucinations).

 They can cause a person with dementia to
misinterpret their environment and what is in it. The consequences of such difficulties can be more
severe for people with dementia than for people without, since they may not know (or remember) that
they are making 'visual mistakes', or be rational or able to 'test reality' accurately. They may also have
difficulty explaining what they have seen.

Visuoperceptual difficulties have been reported for a number of dementias including Alzheimer's
disease, dementia related to Parkinson's disease, Lewy body dementia, and vascular dementia (if
stroke-type damage is on or near to the visual pathway in the brain). Of the various types of dementia,
the visual difficulties in Alzheimer's disease have been most studied to date.

Visual perception is complex since, whether people have good vision or not, they try to interpret and
understand what they see. Sometimes trying to understand what was 'poorly seen' involves making a
'best guess' at what was seen. If what we perceive seems real to us, it can directly affect our
behaviour.

Accurate perception
Although 'vision' usually refers to seeing with the eyes, and 'perceiving' refers to making sense of the
information that the eyes (and the other senses) are receiving, the two words are often used
interchangeably.

To perceive accurately requires the ability to co-ordinate all the components of the visual system
(eyes, optic muscles, retinas, optic nerve) and process information from other senses and thoughts. It
also depends on overall health of the body, visual system and brain, alertness, mood, motivation and
1even the expectation of what 'should' be seen. Accurate vision also requires the co-ordination of every
aspect of our cognitive (thinking) ability to manage and make sense of visual information (Jones G M
M et al, 2006a).

There are many components to vision: adjusting and maintaining optimal focus; adjusting to different
light levels; perceiving depth of field, black and white, colour, lines, objects, faces; distinguishing
between faces; separating objects from background; making the accurate small eye movements
required to follow moving objects and scan information. There are also many possible types and
combinations of visual difficulties.

Advances in the neuroscientific understanding of normal vision are helping to better understand visual
changes resulting from ageing, use of medication, illness or injury, and specific types of dementia.

Normal age-related changes in vision

Visual changes resulting from normal ageing can include:
. reduced visual acuity (sharpness - nearby objects become blurred first)
. an increase in the amount of light needed to see
. an increase in the negative effects of glare
. more time required to adapt to marked changes in light level (from dark to light or vice versa)
. a reduction in size of the peripheral visual field
. decreased contrast sensitivity
. decreased depth perception
. changed colour vision (increased colour saturation required to see colours - gradual loss of the
blue/violet part of the colour spectrum - dark colours and pastel shades become increasingly
difficult to distinguish between)
. changes in the small eye movements (used to track moving objects, orientate oneself in new
locations, and to read)
. blurring from 'floaters' (clumps of cellular debris in the vitreous humour gel in the eye)
. light flashes or momentary distortion of images (when vitreous humour in the eye begins to
pull away from the retina)
. decreased ability to perceive the flickering of strobe lighting.
Most people have regular sight tests and adjust automatically to their changing vision as they get
older. They can use glasses, accurately problem-solve, or learn to compensate for visual changes.
However, people with dementia, increasingly, may not be able to do this.
Illnesses, drugs and medications can affect vision
As well as the effects of normal ageing on the visual system, a number of visual disorders are
commonly associated with ageing. These include cataracts, glaucoma, macular degeneration and
retinal complications from diabetes. These can all result in changes such as blurring, partial loss of
visual field, through to genuine visual hallucinations and complete blindness.
Use of alcohol and other recreational drugs can also affect vision, as can withdrawal from them.
2Sometimes medications can cause or contribute to visual difficulties. A surprising number of
medications commonly taken by older people can have visual side-effects. They include some drugs
from the following categories: cardiovascular, non steroidal anti-inflammatory, antibiotics,
anti-Parkinson, and even eye medications.
Additional visual difficulties in some types of dementia
There can also be additional visuoperceptual difficulties in dementia related to Parkinson's disease
and Lewy body dementia. In vascular dementia, if strokes occur along or near the visual pathway, a
wide range of visuoperceptual difficulties, including hallucinations, can result. Importantly, changes in
vision from strokes may not be noticed by an individual.
Currently, most is known about damage to the visual system in Alzheimer's disease (and 'posterior
cortical atrophy', a rare variant of Alzheimer's disease, see Factsheet 479). The 'plaque and tangle'
damage which characterises Alzheimer's disease, initially accumulates in the brain areas linked to
memory for processing new factual information. It lies close to a part of the visual pathway, which can
also become affected from the spread of plaque and tangles. Later, other parts of the visual pathway
can also be involved. Difficulties in both primary and complex visual functioning have been described
for Alzheimer's disease. (Note that some of these are similar to those described for normal ageing.
However they can occur independently from, or in addition to, normal age-related visual changes and
visual illness.)
Specific difficulties that have been reported in Alzheimer's disease include:
. reduction in number and accuracy of small eye movements
. colour perception (loss of the blue, purple, green part of the spectrum)
. figure-background contrast discrimination
. depth and motion perception
. visual acuity (but not initially)
. object and facial recognition.
Some noticeable consequences of such problems include difficulties with:
. assembling puzzles
. reading books, or doing visual tasks involving close eye movements
. watching TV shows with rapidly moving images.
Less obvious difficulties may involve the ability to:
. play board games
. keep handwriting in horizontal lines
. find objects readily (even though they may be in front of a person)
. copy images accurately
. walk or mobilise confidently.

Evidence for the types and range of visual difficulties that can occur comes from special types of sight
3testing and scans, from people's accounts of their own difficulties, and from careful observations of the
visual errors repeatedly made. These include such things as:
. difficulty re-adjusting one's spatial orientation when moving around (even in familiar
environments like walking in one's own neighbourhood)
. difficulty driving when rapidly changing information needs to be analysed and accurately
responded to
. difficulty judging the height of the floor when the colour flooring changes (colour illusions,
figure-background and depth of field difficulties can make surfaces difficult to judge)
. high-stepping over carpet rods or shadows, thinking they signify a change of level
. difficulty problem solving visual illusion effects (for example, when going downstairs -
determining how many steps there are, and where the next one is; going upstairs is not
usually a problem)
. resisting walking on shiny flooring because it looks wet or slippery
. walking on the darkest patterns (or shadows) of flooring to try to avoid falling
. misinterpreting reflections in mirrors, windows or shiny surfaces (refusal to go into a toilet
because reflections make them appear to be occupied; fear of an 'unknown person who keeps
disappearing' being present)
. mistaking TV images for real people ('little people') because they are brighter and more visible
than a TV console located against a dark background
. inability to find a particular item (eg handbag, clothing) even though the item is in front of a
person and appears to be in their field of vision (this can make it difficult even to locate
someone's hand to be able to return a handshake).
. difficulty in locating people or objects because of other distracting or competing visual
information (such as patterned wallpaper).
. difficulty in positioning oneself accurately to sit down in a chair, on the bed, on the toilet
(difficulty estimating depth of field, especially if the objects are behind a person, out of view;
some people make multiple checks but still have difficulty and may even try to straddle them
from the front. Note that such difficulty may be mistaken for incontinence)
. inability to find objects or places because of a lack of colour contrast (for example, not seeing
there is cauliflower and pasta on a white plate, or not seeing doors painted the same colour as
the walls)
. restlessness from visually over-stimulating environments (eg too many shiny Christmas
decorations in some care settings that can mask important orientation cues).
As seen from the examples above, visual difficulties can affect many aspects of a person's daily
functioning. If people with dementia are living in their own home with carers who are helping them, the
real extent of their visual difficulties may not be apparent until they experience a change in
environment, like going out shopping, on an outing, or on holiday.
Visual difficulties and 'perceived obstacles' can make a person more fearful of falling, and slow down
their movements while they try to walk safely. If carers and companions understand this, they can try
to anticipate situations which will likely pose perceptual difficulties, help explain what is being
encountered, offer their arm for support, offer encouragement, and slow down their own movements
around a person with dementia.
4Categories of visual mistakes
With improved neuroscientific understanding of the visual system, it is possible to categorise different
types of visual mistakes. Some examples are listed below. Although hallucinations are perhaps the
best known, recent research (Jones G M M et al, 2006b) suggests they may be rarer than previously
thought because other categories of visual mistakes have not previously received much attention.
Illusions - a 'distortion of reality' resulting from some physical property or characteristic of the image
(reflection, shiny or bright surface, poor figure/background contrast, timing of presentation, etc).
Example: a person mistook the distorted reflection of a doorstop in a cylindrical, shiny, stainless steel
bin, for there being a 'mouse in the bin'.
Misperceptions - a best guess at inaccurate, degraded or distorted visual information (usually as a
result of damage to the visual system). Misperceptions can be influenced by motivation, previous
experience and expectation.
Example: a dark stain on the carpet was mistaken for a rat.
Example: walking down a long, dark corridor with benches along the wall resulted in a person with
dementia thinking she was at a train station.
Misperceptions of illusions - what is already incorrectly seen, may be seen as even more distorted
by a damaged visual system.
Example: a gentleman who approached a lift that had three large mirrors in it, mistook himself
reflected three times for a crowd of people who would not move to allow him in.
Misidentifications (agnosias) - incorrectly identifying objects and people resulting from damage to
specific locations of the visual cortex.
Example: a gentleman tried to use the black remote control for the TV to shave with.
Example: a mistaken thought that a large statue of a dog was real resulted in food being thrown at it
daily.
Example: inability to distinguish accurately between a son, husband, and brother.
Misnaming what has been seen (or assumed to be present) - this can result from difficulties to
retrieve the nouns and words to describe what is being seen accurately, or from making time
perception errors and using tenses inaccurately.
Example: A collection of metal zimmer frames piled up at the end of the corridor was referred to as
'the robots'.
Example: A lady who was severely disoriented in time thought her children were still young and living
at home. She cautioned her husband as he walked past their old bedroom door, to 'be quiet so you
don't wake the children'.
Hallucination - seeing something when there are no cues for it in the outside world. It is an internally
produced visual image experienced with the eyes open. Sometimes people are aware that what is
being seen is not present in the outside world, and they can stop it at will. Others may not be aware it
is not real and cannot stop it at will. There are many different types of visual hallucinations.
Genuine visual hallucinations can result from urinary, chest or other type of infection, other illness, or a
reaction to medication (see Factsheet 520, Hallucinations in people with dementia). They have also
been more associated with Lewy body dementia, than other types of dementia. This should be
considered if other causes of visual difficulties or hallucinations have been eliminated or treated, and
visual hallucinations persist. (See Factsheet 403, What is dementia with Lewy bodies?)
5Interventions for visuoperceptual difficulties
The increased understanding of visual mistakes is generating new ideas for assisting people with
dementia.
Careful attention to eye care and visual health
. Check that any glasses worn are clean and that the prescription is correct. (For more
advanced dementia, this may require use of special non-verbal tests as for people with
learning difficulties.)
. Arrange for regular eye checks.
. Encourage the person to wear glasses if they need them. Glasses will improve acuity
(sharpness) of what is being seen; however, glasses cannot correct difficulties resulting from
other types of damage to the visual system.
. If cataracts are the cause of, or contributing to, poor sight, talk to a GP about how to have
them treated.
Environmental adaptations
Aiding specific visual functions can help people with dementia (Jones et al, 2008). The first thing to do
is to improve lighting levels. It has been estimated that more than half of British homes do not have
enough lighting even for ordinary visual purposes (Whitfield Grundy, 1992). Improved lighting has
been found to be instrumental in preventing falls, and also in reducing visual hallucinations (Pankow et
al, 1996).
Deliberate use of colour cues can also help significantly. For example, one study with people with
advanced Alzheimer's disease showed that changing to highly visible red cups and plates led to a 25
per cent increase in food intake and an 84 per cent increase in liquid consumption (Dunne et al, 2004).
Brightly coloured toilet doors have also been used successfully in a variety of care settings to help
people with dementia find the toilet independently, and more readily.
High contrast toilet seats (compared to the colour of the toilet fixtures and walls) can make it easier to
locate them. If a person needs handrails choose extra-long ones so that they are as conspicuous as
possible (without the person having to turn their head to look for them).
Some tips for minimising visuoperceptual problems
. Provide good, even lighting (people resist going near dark areas in corridors and rooms).
. Try to eliminate shadows.
. Minimise busy patterns on walls and flooring.
. Use of non-shiny, light-coloured flooring will reflect light upwards and enhance overall ambient
light levels.
. Remove or replace mirrors and shiny surfaces if they are problematic.
. Highlight important object and visual cues (signposting/orientation points).
. Camouflage objects that you do not want to emphasise (eg light switches or doors that people
with dementia shouldn't use).
6. Minimise 'visual obstacles/barriers' such as changes in floor surfaces or patterns, to assist
independent walking.
. Choose activities to match the person's visual abilities.
For information about a wide range of dementia-related topics and details of Alzheimer's Society
services in your area visit alzheimers.org.uk
Useful organisation
Dementia and Sight Loss Interest Group
Alzheimer's Society, RNIB and the Thomas Pocklington Trust have created the Dementia and Sight
Loss Interest Group. The Interest Group considers connections between loss of vision and dementia,
including difficulty with visual perception that may be related to dementia and other eye conditions
such as cataracts.

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