Parallax in optics has nothing to do with ones eyes. It's simply (only!!!) the target/subject image not being focused by the front lens at the focus point of the back lens. Moving the back lens (eyepiece!!!) on a rifle scope only moves its focus point front to back across the reticule (or image thereof).
Parallax happens with binoculars when the eyepieces are not moved in/out such that the subject image is sharp.
It's all exactly the same with a single lens reflex camera. Adjusting the front lens (that thing fit to the front of the camera) focuses the subject image on the ground glass focusing screen (just like the reticule in a rifle scope). Then you adjust the camera eyepiece diopter setting so the image on the ground glass is sharp and clear; usually be seeing the fine lines on it appear very distinct and sharp. Then you can focus the front lens to focus the subject image very sharp and clear on the ground glass.
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