Tiny blood vessels behind your eyes can show the health of your brain, a recent study says. Scientists have found that middle-aged people with more dilated veins in the whites of their eyes score worse on intelligence tests.

The study’s lead author, Idan Shalev, said factors such as smoking, diabetes, and even socioeconomic status were not related to a poor score. Shalev said that because of the vessels, the eyes develop from the same cells as the vessels of the brain and they can perfectly reflect his condition.

Research has shown that the health of your eyes can indicate brain health even at a much earlier age. Shalev stated that even if you have good eyesight, the retinal image is much more informative and may be the easiest way to test your brain.