United States: Our eyes can give important clues about the health of our brain. Problems with vision can be one of the earliest signs of brain issues, like dementia. A new study shows that losing sensitivity in our eyesight can predict dementia up to 12 years before doctors diagnose it.
As reported by the Science alert, the study followed 8,623 healthy people in Norfolk, England, for many years. By the end of the study, 537 people developed dementia, which helped researchers understand what might have happened before the diagnosis.
As we began the study, we also had the individuals complete a visual sensitivity test. In the test they were required to push a button when they saw a triangle start to emerge beneath the dancing dots.
Those who would develop dementia were considerably slower to identify that triangle on the screen than the people who would never get dementia.
So why might that be?
Visual symptoms may be the first sign of cognitive deterioration since the neurotoxic amyloid plaques of the Alzheimer’s brain may initially target the vision centers before the memory centers of the brain are affected. Perhaps vision tests can uncover such things earlier than memory tests can.
The next is of is an early cognitive symptom related to Alzheimer’s; the inhibitory control of eye movements is deficient; distracting stimuli appear to exert more control over attention.
Patients with Alzheimer’s disease also appear to have a problem in selective inattention, which may be reflected in problems related to eye movement control.
If dementia reduces the ability to screen out irrelevant inputs, then these difficulties could contribute to an elevated risk of accidents while driving – an area we are presently exploring at Loughborough University.
Recognizing faces
We have some data that indicates that new people’s faces seem to be inefficient when they are being processed by people with dementia. In other words, they do not scan the face of the person with whom they are conversing in the natural manner.
There are other aspects of processing involved in vision that are also compromised in Alzheimer’s disease including: the patient’s ability to see the outlines of objects (contrast sensitivity), the patient’s ability to distinguish between some colours as, for example, a patient has a significantly reduced ability to see colours in the blue-green spectrum early in their dementia and have no idea of it; these areas of visual impairment can undermine people’s lives massively but the patients will not always