system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do nearsighted people need to wear glasses when using VR?

The screen in inches from one’s eyes, where their vision is ostensibly still good. Yet I see prescription lenses being sold to mount inside VR headsets, and general advice of “wear your contacts when using VR headsets. Please help me understand.
gpt
VR headsets are calibrated to project an image that is "correctly" focused for someone with "normal" vision. But this image is a trick; it has to appear to be farther away, which makes the person try to focus like that for realistic graphics. Otherwise, anyone who used VR for any extended period would get eye strain as if they were reading a book inches from their face.

Someone with nearsightedness doesn't have that ability, so even though the screen is inches away, it's projecting an image that is like it's farther away which makes it blurry.