We often hear that looking at distant objects after staring at screens is good for the eyes to prevent strain.

But from the perspective of eye muscles, what is the difference between small font that is up close on a screen and a poster with large words on it say 30 meters away?

Since if something grows in size as it travels away from you - from your perspective theres no way you could perceive it as moving away from you.

Doesn't the eye still have to focus in the same way, so why then why would looking at objects 30 meters away act as a way to counter strain from looking at smaller font closer up if they are two sides of the same coin?

  • $\begingroup$ Welcome to Biology.SE. Please clarify your question. It seems to be about focal length, which is really a physics question. Perhaps you are trying to ask about how the eye changes focal length — if so, please do some research on your own and then ask specific questions about what is still unclear to you. Also, it is unclear what perception of movement (paragraph 3) have to do with the rest of your question. In general, questions on this site must: demonstrate prior research, be clear, be specific, and be about biology as defined in the tour. ... $\endgroup$
    – tyersome
    Jul 5 at 18:06
  • $\begingroup$ ... You will have a better experience on this site if you familiarize yourself with the expectations by consulting the help center starting with How to Ask, what is on-topic, and what is not. Thanks. $\endgroup$
    – tyersome
    Jul 5 at 18:09
  • 3
    $\begingroup$ I don't see how this question does not fit here even after reading those links...its not about focal length in terms of physics its about how the eye perceives distance in order to adjust its focus. How can the eye tell the difference in order to make the statement that looking at long distances relieves eye strain from looking at short distances from the example i gave. $\endgroup$
    – WDUK
    Jul 5 at 20:09
  • $\begingroup$ I did but I am not finding any solid answers other than physics equations but thats not really answering how the eyes/brains interpret it. @Laura_Jonees $\endgroup$
    – WDUK
    Oct 2 at 0:37
  • $\begingroup$ I suggest you do some background research on optic first because your premise is way off. $\endgroup$
    – John
    Oct 2 at 21:28

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