I have myopia so I wear corrective lenses. One set of glasses I have is designed to focus from about 2 feet to infinity. I can see the dashboard of a car, but I can also see buildings at long distances and they look sharp and in focus.

However, when I look at the night sky, the stars do not seem to be perfectly in focus. Is this just the normal atmospheric disturbances distorting the starlight, or are my lenses imperfect for objects at stellar distances? In other words, is there a difference between a corrective lens that focuses from 2 feet to infinity and a lens that is designed to focus only at infinity?


1 Answer 1


The corrective lenses you have are fixed at a particular power. The range of distances available to you is due to accommodation. There is no such lens that allows you to focus at only one distance (assuming you have an otherwise healthy optic lens).

Your prescription will generally be set with your eye able to have the sharpest focus at infinity when relaxed. However, this focus will not be perfect.

When you have a dense visual field (very normal in your daylight environment), any aberrations in your visual system that create small reflections are overwhelmed by the signal from the environment. When looking at stars, these aberrations are very visible against the black background.

Further, at night with the low total light level, your pupil is maximally dilated. This larger aperture increases the opportunity for problems to be visible. (If your pupils were pinholes, your vision would be sharper, but the light collected would be insufficient).

So while you may have the correct spherical correction for distance vision, there will be other, smaller problems that are not corrected by your lenses, and these problems will be easier to see when looking at stars than when looking at something in the daytime.


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