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

首先，不要长期盯着一样东西。

youdao

Indoor and outdoor sports activities both make the eyes focus on more distant objects, which prevents the eyes from changing shape.

室内和室外运动都能使眼睛集中在更远处的物体上，从而防止眼睛改变形状。

youdao

His eyes slowly began to focus on what looked like a small dark ball.

他的眼睛开始慢慢聚焦到那个小黑球似的东西上。

《柯林斯英汉双解大词典》

"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?