Causes of slight loss in dementia
Sight loss when coupled with dementia isn’t just about not being able to see things around you. These conditions can lead to disorientation, problems with mobility, increased risk of falls, and difficulties communicating, understanding and learning new tasks. In this article we look at WHY a person with dementia might be experiencing problems with their vision, hopefully bringing you one step closer to reducing the impact of sight loss.
As we mentioned in our previous article, Dementia and Vision, sight loss can be as a result of problems with eyesight and/or brain health. This means that someone with dementia could be facing sight loss, despite having healthy eyes. It’s the part of their brain that processes visual information that is damaged as a result of dementia. However, it could also be because of an eye condition like cataract, a health condition like a stroke, or the side effect of a medication like antibiotics. We explore these causes in more detail below.
An eye condition
- Age related macular degeneration: This condition affects the central part of your vision which makes objects in the middle of your vision blurry or distorted. It can make things like reading and driving difficult.
- Cataract: This condition causes the lens of your eye to become blurry or clouded. Bright light and glare makes it even more difficult to see. It can make colours look faded. People with cataracts find it difficult to read signs and affect their ability to drive as key features in their vision start to merge. It is possible to operate on cataracts.
- Glaucoma: This condition causes a person to lose part of their visual field and/or visual acuity. They experience tunnel vision where areas of their vision are completely blank. Too much bright light is painful, reduces vision and the person starts to see rainbow coloured circles. It can make getting around difficult, where the person constantly misses objects on the floor.
- Retinitis pigmentosa: This is a rare genetic condition that can also cause tunnel vision where only a tiny window of central vision remains. While a person with this condition might be able to read 20/20 letters, because of their small field of vision, they are practically become blind. It gradually and progressively leads to sight loss.
- Charles Bonnet Syndrome (CBS): This condition causes visual hallucinations, where people start to see things that aren’t there. Because this is also a symptom of dementia, it can be missed. It’s important to get a diagnosis to make sure the symptoms aren’t caused by dementia. CBS is common among people who have lost their vision from an eye condition.
As you can imagine, the onset of an eye condition can make coping with existing symptoms of dementia more difficult. It could even exacerbate it. But remember, these conditions can be tested for and most of them can be treated.
A health condition
- Diabetic retinopathy: People with diabetes can lose areas of their vision and sharpness of their visual field, causing their vision to be blurry and patchy.
- Stroke: Vision problems are common after a stroke. When a stroke occurs, the brain is deprived of oxygen, which could damage areas of the brain that processes visual input as well as visual pathways between the eye and the brain. This impacts both vision and perception.
- Nutrient deficiency: Nutrients important to vision include Vitamin A, D, C, E, B12, and zinc. Vitamin A plays the most significant role, where severe vitamin A deficiency can lead to xerophthalmia, a condition that can result in blindness. Research suggests that diets rich in vitamin A is associated with a reduced risk of cataracts and age-related macular degeneration.
Dementia can disrupt areas of the brain that are responsible for the way we perceive and process visual information. Studies have shown that people with dementia can have changes in vision and processing of visual input despite healthy eyes. The problems that can occur as a result of dementia include:
- Depth perception, where it is difficult to tell if something is two dimensional or three dimensional. There are also problems judging heights and distances between objects and people.
- Misinterpretations, where there is lack of visual acuity and distinguishing between contrast in colours. This makes it difficult to identify objects amongst it’s background.
- Hallucinations, where they see things that aren’t there.
There are specific types of dementia that tend to cause damage the visual system and lead to visuoperceptual difficulties:
- Alzhiemer’s disease makes it difficult to detect different colours, especially on the blue spectrum, movement, objects and faces.
- Parkinson’s disease affects general mobility, which includes movement of the eyes. This can make it difficult to focus in on objects and see things clearly up close. It can also impact the ability to sense individual colours, as they tend to appear duller. Eyelids and blinking rates can also be impacted, causing dry eyes and blurriness.
- Lewy Body Dementia affects the processing of visual input leading to visual hallucinations and vision-related behavioral symptoms ( i.e. visual agnosia, which is when a person can see but isn’t able to recognise or interpret visual information).
- Vascular dementia can have a direct impact on vision, similarly to Alzhiemer’s
- PCA – Posterior Cortical Atrophy (PCA), which is a rare form of dementia that causes visual problems. A person with this condition usually has challenges seeing more than one thing at a time.
Side effects of medication
Blurred vision can be a result of side effects of certain medications like cardiovascular drugs, steroidal anti-inflammatory drugs, antibiotics, and medication for Parkinson’s (anticholinergic medications, such as Artane used to treat tremors). Many of these are commonly taken by older people and can further compound the difficulties that people experience with dementia. Because these medications can affect vision, it’s important to take a list of medications to the eye appointments. Make sure to check with your doctor whether any of the medication could affect the ability to see.