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Message: <blockquote data-quote="PeterPS" data-source="post: 3652971" data-attributes="member: 124043">Henry:I believe that would be true only for some forms of regular astigmatism, but not for oblique or irregular astigmatism.That's an interesting possible explanation. I'll try to test it as you suggest below(I hope the OP will test your explanation too and will let us know if the effect vanished). If your explanation is true that would mean that the effect is a general one, which begs the question why it was almost never reported.Peter.</blockquote>