Monique Keiran: Eyes might show indications of Alzheimer’s

Scientists have determined during the last decade that expansion of a person’s pupils can indicate interest, stress, problem-solving and even arousal. The change in size is usually subtle — a far cry from what happens to pupils when lights dim in a room. However, most humans are able to detect it, often without consciously noticing it.

As well, Swedish research suggests the structure of colours and patterns in a person’s irises apparently may reveal more about our personalities than we are aware.

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The scientists found a relationship between the densely packed lines that radiate outward in a person’s irises and greater warm-heartedness and trust in that individual’s character. They also found that people with more lines curving around the irises’ outer edges when their pupils dilate may tend toward greater impulsiveness and neuroticism.

The genes that determine iris structure might also help shape the brain’s frontal lobe, which influences personality. For example, a mutation in a gene that helps to control development of irises in embryos is linked to impulsiveness and poor social skills.

Now medical professionals are looking more closely at the eyes to see if they provide windows to the early stages of Alzheimer’s disease.

A few years ago, researchers in California discovered that the plaques associated with Alzheimer’s disease occur not only in the brain but also in the retina, the light-sensitive area at the back of the eye. Scientists are working on developing a non-invasive test to detect those retina plaques before they start accumulating in the brain.

The test, which is still in development, requires people to take a supplement of curcumin, the ingredient in turmeric that gives the spice its bright yellow color.

Curcumin binds to beta-amyloid, the protein plaques that form in brains afflicted with Alzheimer’s disease, and “stains” the plaques with a specific chemical signature. A device developed by the researchers allows them to detect the stained plaques in the eye.

Preliminary results suggest that plaque levels detected in the retina correspond to brain-plaque levels detected by brain scans. The retina test also accurately identified every study participant with Alzheimer’s and more than 80 per cent of those without.

As well, longer-term studies track increases in retinal plaque over time, which suggests the technique could also prove useful as a way to monitor patients’ responses to treatment.

Other researchers are developing a different system that detects Alzheimer’s-related plaques in the eye’s lens. Instead of requiring supplements, the lens test uses a plaque-binding substance that can be applied as an ointment to the eye. A special laser scanner is then used to detect the protein.

This system allowed researchers to distinguish 85 per cent of study participants with Azheimer’s from those without. The plaque levels detected in the eye lenses also matched results obtained through brain imaging.

If either of the eye tests makes it past clinical trials, they could become part of adults’ regular visits to their doctors.

Currently, the screening tests used most often to determine Alzheimer’s cases usually detect the disease only after it has already impaired memory and brain function, when treatment comes too late to halt the disease’s progression.

The two main methods used to accurately measure amyloid-plaque levels in the brain during the disease’s early stages include brain scans and collection of fluids from deep within the spine.

Because the scans are radioactive, spinal-fluid collection is painful and both are costly and come with risks, they are used less often.

Easy, non-invasive eye tests for amyloid plaques would provide windows to the progression of this debilitating disease.

And if such tests permit early detection, early treatment might help to prevent the brain’s decline due to the disease.

This could enable the eyes to remain windows on thoughts, interest, mental stress, problem-solving and arousal for much longer in people at risk for developing Alzheimer’s disease.

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