This test that can help you to find out if your viewing distance is appropriate based on your vision. Here is the test:
If this text is more clear to you than the green one, then your myopia is under corrected at your current viewing distance.
It's okay to have it sligthy under corrected.
If this text is more clear to you than the red one, then your myopia is over corrected at your current viewing distance.
Try sit a little bit further.
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It's chromatic aberration: red and green lights from the same distance end up differently in the eye.
The common reason is that you have uncorrected astigmatism. Also note that this is a test about optical refraction. We asume you have a heathy retina and optic nerve system.