Originally Posted by
shanbaum
I can't say whether "most systems" were doing it, but we were surfacing on blank center when I started full-time in the lab 35 years ago. As was the case then, it's still possible to have an off-center grinding pattern that will induce prism, and that's something I saw frequently when I was doing consulting back in the 1980's (which is not to say that's not a "serious" problem - just a common one).
One factor that may diminish the untoward effects of a badly maintained cylinder machine is lens size - back in the very old days (mid-60's for me), we blocked most lenses on PRP (though of course we didn't call it that back then), but the lenses were so small that they stayed fully engaged on the laps, even when the strokes weren't centered.
So, zhutchinscec, we're down to minus lenses only (but not very minus), invariably base out. And that's OU?
When you run your plano test, do three tests - one each with 4, 6, and 8 base lenses.
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