Wednesday, 30 September 2015

Dementia and Vision Problems

Dementia and Vision Problems
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 diseaseLewy 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 even 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. Sometimes 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, seeFactsheet 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.
Dementia and Vision Problems
Evidence for the types and range of visual difficulties that can occur comes from special types of sight testing 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.
Categories 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?)
Interventions for Visuo-perceptual 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 minimizing visuo-perceptual problems
·         Provide good, even lighting (people resist going near dark areas in corridors and rooms).
·         Try to eliminate shadows.
·         Minimize 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 emphasize (eg light switches or doors that people with dementia shouldn’t use).
·         Minimize ‘visual obstacles/barriers’ such as changes in floor surfaces or patterns, to assist independent walking.
·         Choose activities to match the person’s visual abilities.