You may be wondering why I have chosen to write about the above. The reason is twofold. First and most obviously, the number of people in the UK with Alzheimer's disease is estimated at 850,000 and predicted to rise to over 2 million by 2051. Secondly, both this and other forms of dementia can impact on sight. Early detection is important to try and provide good quality of life after diagnosis and reduce pressure of public and private finances. Detection rates for Alzheimer's disease and other dementias are poor with as much as 91% of mild dementia reported as going unrecognised in primary care.
About 60% of dementia sufferers have Alzheimer's disease caused by damage to the nerves in the brain. We believe this process begins some 20-30 years before symptoms such as memory loss and problems with orientation and language begin. The next largest group is vascular dementia caused by problems with the blood supply within the brain, often a series of small strokes. This causes difficulty with thinking and forward planning. There may be also be personality changes and depression together with difficulty concentrating. Around 10-15% of dementia is caused by Lewy bodies which are small protein deposits within brain nerve cells interrupting their connections. Symptoms here may mimic the movement (motor) problems of Parkinson's disease and the thinking impairment of Alzheimer's disease, but also include delusions and hallucinations. People do present with mixed dementia i.e. changes consistent with both Alzheimer's and vascular dementia.
Visual problems due to dementia are quite variable with some particularly affected and others not at all. Some may present for eye tests with problems not linked to eyesight, but due to problems related to early dementia. Naturally, some with dementia will have difficulty describing their symptoms, while some will just submit to visual loss due to progressive dementia. While suffering from the same ageing eye disease as everyone, they may endure failure of higher visual processing like reading, identifying objects and interacting with the world around them. Falls are more common in those with dementia and we know that this is due to many factors, but reduced depth perception in this group has been considered a contributory factor.
It is beyond the scope of this article to detail research, but studying anomalies with eye movement (tracking) has been fundamental to gaining some insight into the impaired visual function of this group. We all have to make the correct eye movements to react to the world around us and this has evolved to allow us to bring objects into a correct and stable focus in our eyes. There is undoubtedly a higher presence of visual impairment amongst dementia sufferers, a problem compounded by their inability to express their symptoms. They have more difficulty identifying common things and sometimes recognising people they know. There may be problems with negotiating around a room, going up stairs, parking or just putting things down correctly. Reading may become slow and laboured with a loss of understanding for what words mean or what's coming next.
Part of my work today and in future will be to try and identify the type of visual problems those with dementia may suffer with and do what I can to address the problems with advice and spectacles where appropriate and referral to further care when necessary.