How does the eye know when the image is in focus? There is distance measuring device, only light entering the eye. No outer feedback to be sure that focus is in fact focus not something the eye think is focus.

Question

Thank you all for your respons and upvotes.

I can now see and focus on the answer of my question 🙂

In: 3993

Answer 1

There is continuous feedback from the brain, which guides the focusing in the eye. Without that, you’re right, the eye doesn’t “know” what to focus on. To see this, look at an object that’s close to you. Now, without changing your head or the direction you are pointing your eye, you can focus on an object in the distance. It’s your brain that is telling the eye what to focus on.