Firstly, do not focus eyes on something for a long time.

首先，不要长期盯着一样东西。

youdao

"You have to concentrate your eyes to something near, but focus your eyes on something far."

VOA: standard.2010.02.21

Then, as we focus our eyes on the Arab region, London, that bastion of order, goes up in flames to gangs of youths and looters.

BBC: African viewpoint: Caged comeuppance?

Our eyes are used to converging on the same spot we're focusing on, but stereoscopic screens force our eyes to focus on a point several inches in front of the convergence point.

FORBES: Adventures in the Third Dimension

Focus your eyes and attention on one place.

FORBES: Could You Be Sued for the Sound of Your Voice?