Astigmatism question

[Dr Jekyll]

Is it possible for someone to have such a weirdly shaped eye that not only are they astigmatic, but when their pupil widens in the dark their astigmatism changes? A friend of mine is convinced that though her corrected vision is 20/20 in daylight, things get blurred after dark to the extent that she really needs a different prescription. I reckon her prescription was slightly out and the dark makes focusing more critical, but she always insists not.

[HelenT]

It was suggested that some people have a short sighted shift in prescription in low light and it was widely discussed in the optical press a few years ago but seems to have fallen out of favour.Low astigmatic or under corrected prescriptions will cause more problems in poor light as the pupil is larger so the light does not focus as well onto the back of the eye(conversley looking through a pinhole will bring the light into a sharper focus onto the retina)