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. [’Eye’ Can’t Look: 9 Eyeball Injuries That Will Make You Squirm].