I don't mean it's literally bad for your eyes - there may well be benefits to constantly shifting your gaze/focus/etc. I can't comment on that.
I'm talking about "natural" eye movement being a well-known design principle. This means that eyes very naturally follow a Z pattern that doesn't exceed the periphery of your focus. So if you load up a fresh page, your eyes will naturally look top left -> top right -> bottom left -> bottom right, bounded by your standard viewbox (which is about 800px-1200px wide at 96dpi and 1-2ft, the standard distance most people sit from their monitor). So you usually stick your most important information along that pattern. Anything outside this boundary requires an extra "look", which means a slight hesitation/delay on the part of the user. That's not to say the space is unusable, just that you put your most common/important features/information along this flow.
It's also not an ironclad rule, but it does work very well. When I went to the old GitHub, my eyes always followed the same pattern: repository name (top-left, to make sure I was on the right page), account (verifying that I'm logged in), branch, clone/download, then file list or more commonly, the README (bottom-left). It was a very quick, natural way to navigate a random GitHub page.
Now, I literally have to move my head to do this. The weighting also feels completely unbalanced, like there's too much information on the left it's all slanting in one direction.
I'm talking about "natural" eye movement being a well-known design principle. This means that eyes very naturally follow a Z pattern that doesn't exceed the periphery of your focus. So if you load up a fresh page, your eyes will naturally look top left -> top right -> bottom left -> bottom right, bounded by your standard viewbox (which is about 800px-1200px wide at 96dpi and 1-2ft, the standard distance most people sit from their monitor). So you usually stick your most important information along that pattern. Anything outside this boundary requires an extra "look", which means a slight hesitation/delay on the part of the user. That's not to say the space is unusable, just that you put your most common/important features/information along this flow.
It's also not an ironclad rule, but it does work very well. When I went to the old GitHub, my eyes always followed the same pattern: repository name (top-left, to make sure I was on the right page), account (verifying that I'm logged in), branch, clone/download, then file list or more commonly, the README (bottom-left). It was a very quick, natural way to navigate a random GitHub page.
Now, I literally have to move my head to do this. The weighting also feels completely unbalanced, like there's too much information on the left it's all slanting in one direction.