Dementia and vision problems (visouperceptual difficulties) may occur for many reasons. Normal aging, other medical conditions of the eye and damage to different parts of the visual system from different types of dementia are all common causes that must be considered when working with a person with dementia.
The person with dementia and vision problems can present differently by each individual. These “vision problems” may include a person seeing illusions, having misperceptions, misidentifications and even hallucinations.
The result of these “vision problems” can be more severe for a person suffering with dementia than for an individual without dementia. This is because a person with dementia may not understand (or remember) that they are having “vision problems”, or have the ability or be a able to rationalize and “test reality” accurately.
Dementia and vision problems have been reported for a number of types of dementias including: Alzheimer’s disease, dementia related to Parkinson’s disease, Lewy body dementia, and vascular dementia . With vascular dementia vision problems may occur if stroke-type damage occurs on or near the visual pathway in the brain.
Studies of Alzheimer’s dementia with vision problems has been most studied of all the dementias to date.To help you to better understand what may be occurring with your family member with dementia, you must first understand the complex nature of the visual perceptual issues your family member may have.
Simply put, when a person sees something they must interpret what they see and then understand and process that information. Whether a person with dementia has good vision or not, they may try to understand what is seen, and make a “guess” at what they are seeing. What a person “sees” and then interprets they “see” can be very different from reality. However, it is their reality, and does affect a persons behavior.
What is accurate perception?
This is a term that refers to a person seeing with the eyes and then ‘perceiving’ or interpreting the information with their eyes and the other senses are receiving.
A person without dementia, has the ability to co-ordinate all the parts of the eye system, (including the eyes, optic muscles, retinas, and optic nerve) and process the information from the other senses. There is also a cognitive process that must occur in this process that requires the coordination of make sense and process what was seen.
In a person with dementia and vision problems, this “perception” will depend on the visual system and brain connections, the mental alertness of the person, their mood, even the of the person’s expectation of what they ‘should’ be seeing.
There are many different components to the eye and sight process. The eye must adjust and maintain optimal focus; adjusting to various and changing light levels; perceive the depth of field, determine white and black, identify colors, lines, objects, and faces; identify and distinguish differences for facial recognition; separate objects from the background. The eye must also make small and accurate eye movements to follow moving objects and then that information into the brain.
An aging person may experience 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 injury, illness or medication, and specific types of dementia.
Normal Age-related Changes in Vision
Visual changes resulting from normal aging 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 color vision (increased color saturation required to see colors– gradual loss of the blue/violet part of the color spectrum– dark colors 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 humor gel in the eye).
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. People with dementia, increasingly, may not be able to do this.
Illnesses, Drugs, and Medications Can Affect Vision
As the effects of normal ageing on the visual system, a number of visual disorders are commonly associated with aging.
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.
Sometimes medications can contribute or cause to visual difficulties. A surprising number of medications commonly taken by older people can have visual side-effects.
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.
Specific difficulties that have been reported in Alzheimer’s disease include:.
- reduction in number and accuracy of small eye movements.
- color 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 confidently.
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 able or rational to ‘test reality’ accurately.
As the effects of normal aging on the visual system, a number of visual disorders are commonly associated with aging.
These can all result in changes such as blurring, partial loss of visual field, through to genuine visual hallucinations and complete blindness.
In vascular dementia, if strokes occur along or near the visual pathway, a wide range of visuoperceptual difficulties, including hallucinations, can result. They can occur independently from, or in addition to, normal age-related visual changes and visual illness.).