Came across a youtube video by Chris Sajnog where he has some exercises to focus your eyes for fast sight acquisition. I thought it was really cool how you can get immediate feedback on it working.  

Here are 2 optical illusions he uses.

This image, simply focus until everything stops spinning. try holding it like that. continue exercise until you can control the spinning instantly when looking at sight.













On this image, same thing. Focus on the sights.  You are fully focused when the magenta circles completely disappear.  More you train with this the faster your eyes will get a focused on the sight picture.

Amazing!

for me nothing is spinning in the first pic

and the second pic the magenta dots never go away

No spinning on first and magenta dots never go away either.

Seriously?  This things spin even just glancing at them for me.  But if i give it a little focus they stop.  The magenta circle (for me) does go away, or mostly gone If I really focus on the sight picture.  I am on a laptop. maybe the large screen helps?