People with the rare and fatal brain disorder Creutzfeldt-Jakob disease (CJD) show signs of the disease in their eyes, according to a new study. The study found evidence of prions — the infectious proteins that cause the disease — in the eyes of nearly a dozen patients with CJD.
The findings suggest that patients’ eyes could potentially provide a “window” to the brain that may help researchers diagnose the disease early if new eye tests are developed. The results also raise concern about the potential for the disease to spread through routine eye exams or eye surgeries, during which equipment could become contaminated with prions, the researchers said.
Creutzfeldt-Jakob disease is a progressive neurological disorder that affects only about 1 in a million people worldwide each year, according to the National Institutes of Health (NIH). The disease, which is related to “mad cow disease” in cows, is caused by prion proteins that fold abnormally, leading to lesions in the brain. The most common form of CJD is sporadic, which means that the disease does not appear to have a genetic or an environmental cause.
There is no treatment or cure for CJD, and the condition usually results in death within one year of diagnosis. Previously, a small number of patients with CJD were found to have prions in their eyes. But it was unclear how common this occurrence was, or how widespread the prion proteins are throughout the eye. In addition, these earlier studies were done before the development of more sensitive tests for prions that are available today.
In the new study, the researchers analyzed the eyes of 11 patients who died from sporadic CJD and agreed to donate their eyes for research. The study is the largest to date to examine CJD patients’ eyes for prions.
The researchers detected prions in the eyes of all 11 patients. What’s more, they found prions in all eight regions of the eye that were tested, including the eye’s cornea, lens, ocular fluid, retina, choroid (a part of the eye that contains blood vessels and connective tissue), sclera (the white of the eye), optic nerve (which connects the back of the eye to the brain) and extraocular muscle (which controls eye movement.)
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. Currently, the only way to confirm a diagnosis of CJD is to test a sample of brain tissue after a person’s death.
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