Detecting Alzheimer's Disease through the Eyes?

Alzheimer's Disease International estimates that the number of people living with dementia worldwide - nearly 44 million in 2014 - will almost double by 2030 and more than triple by 2050.

There is no single test that can show if a person has Alzheimer's, but doctors can almost always determine if a person has dementia, although it may be difficult to determine the exact cause. Diagnosing Alzheimer's requires careful medical evaluation, neurological testing, and sometimes brain imaging and blood tests to rule out other causes of dementia.

Most of the testing for early disease - MRI scans of the brain, brain PET scans looking for amyloid, and spinal taps looking for certain proteins in the spinal fluid - are not very accurate, and they are invasive and often expensive.

Researchers have now turned to findings in the eye to help with early detection and are hoping to find ways to make the diagnosis earlier when potential treatments may have a better outcome. There is also hope that these tests will be less expensive and invasive then the other options.

One of the tests that has shown promise is an OCT of the retina. Almost every eye doctor’s office already has an OCT, and so if this research proves fruitful, the test could be done relatively cheaply because there is not a need to buy more expensive equipment. The average OCT exam costs much, much less than the cost of an MRI or PET Scan.

Neuroscientists at the Gladstone Institutes in San Francisco showed a proof of concept in frontotemporal dementia, which is like Alzheimer’s but attacks much earlier and accounts for just 10% to 15% of dementia cases. They found that patients with frontotemporal dementia had thinning of the neuron layer of the retina on OCT.

In a study at Moorfields Eye Hospital they also found that people who had a thinner layer of neurons in the macula on an OCT exam were more likely to perform poorly on the cognitive tests - a clear warning sign they may be undergoing the early stages of dementia.

Study leader Dr. Fang Ko, said: “Our findings show a clear association between thinner macular retinal nerve fiber layer and poor cognition in the study population. This provides a possible new biomarker for studies of neurodegeneration.”

A second marker that is getting a careful look is identifying the presence of amyloid in the eye. Amyloid, thought to be one of the key causes of Alzheimer’s, which makes up most dementia cases, is often found to have formed into clumps and plaques in the brain. Scientists at Waterloo University in Canada found people with severe Alzheimer’s disease had deposits of a protein amyloid on their retinas.

Research conducted at Lifespan-Rhode Island Hospital in Providence co-led by Peter Snyder, a professor of neurology at Brown University, and Cláudia Santos, a graduate student at the University of Rhode Island, is attempting to detect amyloid in the retina by OCT and follows people over time to see if the amyloid increases and if it correlates with cognitive impairment.

Another angle being pursued by a company called Cognoptix is looking for amyloid in the lens of the eye. Using Cognoptix's SAPPHIRE II system, which detects amyloid in the lens, a 40-person Phase 2 clinical trial was conducted at four sites. The study recruited patients who were clinically diagnosed with probable Alzheimer’s disease (AD) via a rigorous neuropsychological and imaging workup. The study, using age-matched healthy controls, showed outstanding results of 85% sensitivity, and 95% specificity in predicting which people had probable AD.

The company planned a Phase 3 study that must show a strong correlation in a bigger study group to obtain ultimate FDA approval.

One of the other items I was going to include in this post was information on what visual symptoms occur in dementia patients and how family and friends can support them but I found an outstanding review already available online by the Alzheimer’s society that covers all those points. If you have a loved one with dementia this is an excellent read and I highly recommend you take the time to review it.

 

Article contributed by Dr. Brian Wnorowski, M.D.

The Benefits of Daily Disposables

When soft contact lenses first came on the scene, the ocular community went wild.

People no longer had to put up with the initial discomfort of hard lenses, and a more frequent replacement schedule surely meant better overall health for the eye, right?

In many cases this was so. The first soft lenses were made of a material called HEMA, a plastic-like polymer that made the lenses very soft and comfortable. The downside to this material was that it didn’t allow very much oxygen to the cornea (significantly less than the hard lenses), which bred a different line of health risks to the eye.

As contact lens companies tried to deal with these new issues, they started to create frequent-replacement lenses made from SiHy, or silicone hydrogel. The oxygen transmission problem was solved, but an interesting new phenomenon occurred.

Because these were supposed to be the “healthiest” lenses ever created, many people started to overwear their lenses, which led to inflamed, red, itchy eyes; corneal ulcers; and hypoxia (lack of oxygen) from sleeping in lenses at night. A new solution was needed.

Thus was born the daily disposable contact lens, which is now the go-to lens recommendation of most eye care practitioners.

Daily disposables (dailies) are for one-time use, and therefore there is negligible risk of overwearing, lack of oxygen, or any other negative effect that extended wear (2-week or monthly) contacts can potentially have. While up-front costs of dailies are higher than their counterparts, there are significant savings in terms of manufacturer rebates. In addition, buying contact lens solution is no longer necessary!

While a small minority of patient prescriptions are not yet available in dailies, the majority are--and these contacts have worked wonders for patients who have failed in other contacts, especially those who have dry eyes.

Ask your eye care professional if dailies might be the right fit for you.

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