Why is it easy to cross eyes inward (towards nose) but not outward?


Why is it easy to cross eyes inward (towards nose) but not outward?

In: Biology

Because when you cross your eyes inward you can focus both of them on your nose. Which is what they’re designed to do. You can’t focus your eyes on two separate objects at once, as you would need tot to cross them outwards

The muscles that control your eye movements (six of them for each eye) are not under individual control. There are different areas of your brain which control the movement of BOTH eyes in certain directions–this is what keeps them focused on the same object and prevents double vision.

For example. If you want to look to RIGHT there is a part of your brain that activates the muscles that turn both of your eyes to the right (more specifically, it activates the right eye’s lateral rectus muscle which moves your right eye away from your nose and the left eye’s medial rectus muscle which moves it towards your nose.

Separate areas of your brain are responsible for staring at the tip of your nose, looking up, looking down, etc.

Technically, the way you move your eyes outwards is by looking at an object in the distance. If you focus on the tip of your nose, your eyes are crossed. Now shift gaze to a distant object. During that time you eyes *are* moving away from eachother, but the movement is limited.

When people have damage to different parts of their brain, specific eye movements can be lost. For example, if you damage an area of your frontal lobe, you can lose the ability to look right (which involves your left eye moving towards your nose) even though you could *still* stare at the tip of your nose (which also involves moving your left eye towards your nose).