Your Eyes May Show Early Signs of Alzheimer’s: Study

According to recent research, early signs of Alzheimer’s disease may be visible in changes to the retina and optic nerve. It is believed that if detected early, treatments to slow the degenerative condition might be more effective. The retina is a thin layer of tissue at the back of the eye that contains cells that detect light and transmit visual information to the brain.

Research suggests that changes associated with Alzheimer’s, such as the formation of amyloid plaques, could start a decade or more before the onset of symptoms such as memory loss. This period is often referred to as “preclinical Alzheimer’s disease” and is believed to start 10 to 15 years before patients develop symptoms of the disease. It can take four to eight years for Alzheimer’s to progress to its latest stages, by which time moderate levels of the disease have already formed.

To determine how Alzheimer’s could be detected in the eyes, researchers studied donated tissue from the retinas and brains of 86 people with different levels of cognitive decline. They compared this with samples from individuals with normal cognitive function. The research revealed that the retinas of patients with Alzheimer’s disease and mild cognitive impairment showed significant overabundance of amyloid beta protein, a hallmark of the condition.

Moreover, these changes were also detectable in individuals who appeared to be healthy, making this an early predictor of cognitive decline. Changes to the retina and optic nerve corresponded with the pathological stage of Alzheimer’s disease, as well as patients’ mental status. However, it is important to note that these techniques are still in the early stages of development, and more research has to be carried out to verify their effectiveness in detecting Alzheimer’s disease.

How the Current Eye Tests Help Detect Alzheimer’s

Currently, there is no single test that can determine if an individual has Alzheimer’s disease. The retina, an extension of the brain, could be used for noninvasive monitoring of the central nervous system. There are several tests that doctors can use to detect Alzheimer’s disease risk based on the eye’s reaction to a stimulus, or changes to its structure.

Optical Coherence Tomography (OCT)

OCT is a noninvasive imaging technique that captures highly detailed images of the retina using light waves. It can be used to detect changes in the thickness of the retinal nerve fiber layer, which may be indicative of Alzheimer’s disease patients.

Glaucoma Exam

A routine glaucoma exam also offers clues to an individual’s risk for cognitive decline. Patients with normal tension glaucoma have a 52% greater likelihood of developing Alzheimer’s disease.

Ultra-Wide Field Fundus Photography

Fundus photography refers to taking a magnified photograph of the back of the eye, including the retina and optic nerve. A pilot study published in Ophthalmic Research revealed that this can detect eye changes associated with Alzheimer’s disease.

Pupillometry

Pupillometry measures changes in pupil size in response to light. Researchers have found that Alzheimer’s patients have a slower response to light changes than healthy individuals. This could be due to changes in the brain that impair pupil regulation.

The University of California is developing a smartphone app that checks pupil response, which could enable us to check our neurological health, including Alzheimer’s disease risk, at home. However, these techniques are still in the early stages of development, and further research is needed to validate their effectiveness in detecting Alzheimer’s disease.

It is important to bear in mind that these methods do not replace a clinical diagnosis of Alzheimer’s disease. Typically, diagnoses rely on a combination of cognitive tests and medical imaging.