Eye Scan Detects Alzheimer’s Disease

A simple retina scan may soon become a non-invasive method for diagnosing Alzheimer’s disease, and those at risk.

The abnormal proteins that cause Alzheimer’s Disease can build up in the brain two decades before the onset of symptoms and researchers have been searching for ways to detect the disease sooner. Early detection could mean that medications that slow Alzheimer’s progression could be started sooner. The effectiveness of any early treatments could be monitored with eye scans.

Non-Invasive Hi-Res Imaging

Researchers at Duke University and at Washington University School of Medicine in St. Louis have found evidence that Optical Coherence Tomography (OCT) scans can detect the changes in the tiny capillaries and the thinning of the retinal layers in the eye that signal the beginnings of Alzheimer’s disease.

Dr Sharon Fekrat, from Duke University Medical Centre in the US, said: “We’re measuring blood vessels that can’t be seen during a regular eye exam and we’re doing that with relatively new noninvasive technology that takes high-resolution images of very small blood vessels within the retina in just a few minutes.”

Alzheimer’s Causes Retinal Thinning

Microscopic blood vessels form a dense web at the back of the eye inside the retina. In Alzheimer’s patients, researchers saw that that web was less dense, and there was a loss of small retinal blood vessels. The retinal nerve fiber layer was also thinner in patients without Alzheimer’s disease.

Researchers think that reduced levels of acetylcholine in the brain causes some of the symptoms of Alzheimer’s disease. Acetylcholine is one of the neurotransmitter chemicals that nerve cells use to communicate with one another in the brain. Acetylcholinesterase inhibitors prevent the breakdown of acetylcholine and are used to boost the cell-to-cell communication that gets depleted in Alzheimer’s disease.

What is OCT?

Optical coherence tomography is a non-invasive imaging test that uses light waves to take cross-section images of the retina. An OCT shows each of the distinctive layers of the retina. The OCT produces a three-dimensional map of the eye and can show areas of the eye that are abnormal.

The images from an OCT scan are high resolution because they are based on light, rather than sound, as in an ultrasound, or radio frequency, as in an MRI. Because the OCT shows cross-sections of tissues layers, nerve fiber thickness can be measured. 

If you would like to schedule an appointment, please call us (877) 245.2020.

Nader Moinfar, M.D., M.P.H.
Retina Specialist
Orlando, FL

Optical Coherence Tomography (OCT)

OCT, or optical coherence tomography, is another diagnostic test used by a retina specialist. A fluorescein angiogram has been discussed previously and it also provides valuable information about the health of the retina.

An OCT uses light waves to study the different layers of the retina and also provides information about the surface of the retina.

Topography is the study of the surface (in this case the retina) where tomography allows study of a tissue in cross-section.

OCT Studies Retinal Diseases

Common uses for an optical coherence tomogram (OCT) include:

Macular Degeneration
Macular Holes
Macular Pucker
Macular Edema
Diabetic Retinopathy
Retinal Vascular Occlusions (RVO)

The OCT allows the retina specialist to diagnose and problem, but also allows me to evaluate progression of a disease and monitor if a treatment is effective.

For instance, after intra-vitreal injections of VEGF, an OCT allows me to determine if the treatment is reducing the retinal swelling caused by either diabetes or macular degeneration.

Other Uses of OCT

Retinal specialists are not the only ophthalmologists who use this state of the art technology. Using OCT technology to examine the optic nerve is a great way to diagnose and monitor progression of glaucoma.

Performing the Optical Coherence Tomography

The test is painless and non-invasive. No dye or contrast is used. There is no injection (unlike a fluorescein angiogram).

An OCT requires that you are able to sit and place your chin of the machine while keeping your eyes and head very still. A target is provided to keep the eyes still. Nothing will touch your eye.

The whole process takes a few minutes per eye. Usually we prefer the eyes to be dilated. On occasion, very dense cataracts or vitreous hemorrhage (bleeding in the vitreous) prevents a good test result. Remember the test relies on light rays entering your eye. Both dense cataracts and vitreous hemorrhage can block light.

If you would like to schedule an appointment, please call us (877) 245.2020.

Nader Moinfar, M.D., M.P.H.
Retina Specialist
Orlando, FL

Jon Doe