When you close your eyes and focus them on one spot and don’t move them, you start to see grey, like static on a tv. What is that?

Question

When you close your eyes and focus them on one spot and don’t move them, you start to see grey, like static on a tv. What is that?

In: Biology

Answer 1

You can get the same sensation with your eyes open by staring at a spot, although it requires a little more focus.

If your eyes get the same information for a long time, you stop processing that information, so your vision gets replaced by gray blobs wherever the information is being lost.

[More info](https://en.wikipedia.org/wiki/Troxler%27s_fading)