The 20-20-20 rule is a practice to alleviate digital eye strain. The idea is very simple. :-
Every 20 minutes of screen time, take a 20-second break.
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Look at something 20 feet away to relax your eye muscles.
What does the research say about the 20-20-20 rule? The American Academy of Ophthalmology explains that looking at digital devices won’t necessarily damage your eyesight. But it can cause strain and unpleasant symptoms. Humans normally blink around 15 times each minute. When staring at screens, this number decreases to a half or third that often. That can lead to dry, irritated, and tired eyes. Read more..
By the way, I follow this rule as it is the simplest to practice, and I have personally noticed that it helps reduce my eye strain a lot. However, it's hard to make it a habit because you can easily get involved in something interesting and may forget this rule. What I have personally observed is that screen time will never make you blind, but it can make your vision a little hazy. Anyway, this is just one of many rules and practices to protect your eyes. What do you do personally?