Marcus Gunn pupil

Marcus Gunn pupil is a condition that affects your eyes. It is named after a doctor who discovered it a long time ago.

When light enters your eye, your pupil (the hole in your eye) gets bigger to let more light in so you can see better. But sometimes, with Marcus Gunn pupil, one of your pupils acts a bit different from the other one.

So when light shines into the eye with the Marcus Gunn pupil, the pupil doesn't react the same way as the other eye. It may get smaller, but not as much as the other eye, or it may not get smaller at all. This makes one eye look like it's blinking or moving more than the other eye, even if you're not actually moving it.

This condition won't hurt your eyes, and you can still see just fine. Sometimes, it might happen when your eye has been injured or has a certain condition. But sometimes, it can happen for no reason at all.

If you notice that one of your eyes is acting different from the other one, you can tell your eye doctor about it. They can take a look at it and tell you more about what's going on.