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According to a new study, people with Creutzfeldt-Jakob Disease (CJD), a rare and fatal brain disease, have signs of the disease in their eyes.
The study has highlighted prions – the infectious proteins at the origin of the disease – in the eyes of nearly a dozen patients with CJD.
The results suggest that patients' eyes could potentially provide a "window" to the brain that could help researchers diagnose the disease at an early stage, if new eye tests are developed. [‘Eye’ Can’t Look: 9 Eyeball Injuries That Will Make You Squirm]
The findings also raise concerns about the possibility that the disease will spread during routine examinations or sight operations, during which material could be contaminated with prions, the researchers said.
The study, conducted by researchers from the National Institute of Allergy and Infectious Diseases, University of California at San Diego and UC-San Francisco, was published yesterday ( November 20) in the magazine mBio.
Pray in the eyes
Creutzfeldt-Jakob disease is a progressive neurological disorder that affects approximately 1 in 1 million people worldwide each year, according to the National Institutes of Health (NIH). The disease, which is linked to "mad cow disease" in cows, is caused by prion proteins that fold abnormally, causing damage to the brain.
The most common form of CJD is sporadic, which means that the disease does not seem to have a genetic or environmental cause.
There is no treatment or cure for CJD, and this disease typically leads to death within one year of diagnosis.
Previously, a small number of patients with CJD had prions in their eyes. But it was unclear to what extent this event was common or what was the extent of prion proteins in the eye. In addition, these earlier studies were conducted prior to the development of more sensitive prion trials available today.
In the new study, researchers analyzed the eyes of 11 patients who died of sporadic CJD and agreed to donate their eyes for research. The study is the most important to date to examine the eyes of patients with CJD looking for prions.
The researchers detected prions in the eyes of all 11 patients. What's more, they found prions in all eight areas of the eye tested, including the cornea, lens, eye fluid, retina, choroid (part of the eye containing blood vessels and connective tissue) , the sclera (the white of the eye), the optic nerve (which connects the back of the eye to the brain) and the extra-ocular muscle (which controls the movement of the eyes).
The highest levels were found in the retina, the area of light-sensitive cells located at the back of the eye. In some cases, levels of prions in the retina were close to those seen in the brain, the researchers said.
New diagnostic test?
Currently, the only way to confirm a diagnosis of CJD is to test a sample of brain tissue after the death of a person. However, there are ways to diagnose probable or suspicious cases when a person is alive, using analyzes of electrical activity of the brain, brain scans or prion search tests in the cerebrospinal fluid.
Nevertheless, CJD remains difficult to diagnose, in part because the disease can cause a variety of symptoms and these may resemble those of other more common conditions. (Depending on the Mayo Clinic, early symptoms may include anxiety, depression, memory loss, personality changes, vision problems, insomnia, thought disorders, and muscle coordination problems.)
Since high levels of prions have been found in the retina, this discovery "could potentially be exploited for the early diagnosis of prion disease" with some eye tests, the researchers said. For example, an eye test that measures electrical responses in retinal cells may reveal abnormalities in people with CJD, hypothesized. Further studies would be needed to determine how this test or other eye tests could be used to diagnose CJD.
The researchers also noted that about 40% of patients with CJD had ocular symptoms, sometimes early in the course of their disease. These ocular symptoms can lead patients to have an eye exam, which can lead to contamination of the material that may spread the disease. The new discovery "reinforces the recommendations for single-use instruments or other decontamination procedures" as a result of an eye exam in patients with CJD, said the researchers.
Originally published on Science live.
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