The eyes can reveal a lot about the health of our brain. Indeed, problems with the eyes can be one of the earliest signs of cognitive decline. Our latest study shows that a loss of visual sensitivity can predict dementia 12 years before it is diagnosed. Our research was based on 8,623 healthy people in Norfolk, England, who were followed up for many years. By the end of the study, 537 participants had developed dementia, so we could see what factors might have preceded this diagnosis. At the start of the study, we asked participants to take a visual sensitivity test. For the test, they had to …