Do you even know of any physical exercises on your eyes or brain?
Neither have ever been suggested to to me by a medical professional or anyone I trust for advice.
* You use your eyes everyday, and hopefully you're brain, too. That's a good start!
* Don't strain your eyes with excessive periods in front of a screen, take a break.
* As for retaining optimal internal function, keep developing your mind and soul. Read a book, learn a new skill or programming language, or a spoken language. Have interesting conversations with friends or family. Write a story. Make a drawing or painting. Do these sorts of engaging activities in favor of excessive time on repetitive pastimes like video games or YouTube. Try to do the repetitive stuff in moderation when you can.
* Learn to listen to your body.
Just my 0.02
Take care matey.