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Against-the-rule-astigmatism
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Justin
Dec 27, 2001, 6:07:53 PM12/27/01
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What is the difference between against-the-rule astigmatism vs.
with-the-rule astigmatism? Which is more common? I've read two
def. which contradicted one another...
Thanks, Justin
with-the-rule astigmatism? Which is more common? I've read two
def. which contradicted one another...
Thanks, Justin
RM
Dec 27, 2001, 8:52:12 PM12/27/01
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On 27 Dec 2001 15:07:53 -0800, silver...@hotmail.com (Justin)
whined and moaned the following remarkes -:
whined and moaned the following remarkes -:
"With the rule" astigmatism has an axis of about 180 degrees (when Rx
is written in minus cyl form). "Against the rule" astigmatism has
the axis at about 90 degrees.
Both forms are common. Nevertheless, when looking at population
norms, "with the rule is more common in young adults while "against
the rule" is more common in older adults.
Thomas C. Kopan O.D.
Dec 27, 2001, 11:29:40 PM12/27/01
to
With-the-rule means it is usually the case and is considered to be at
axis 180 degrees + or - 30 degrees. (Don't forget the 180 degrees = 0
degrees) . Against- the-rule astigmatism is axis 90 degrees + or - 30
degrees. Everything that is left over (30-60 and 120-150) is considered
oblique astigmatism. Of course, axis refers to the degree location of
the cylinder of an astigmatic lens or astigmatic eye. With is generally
more common. Oblique is usually the least common.
axis 180 degrees + or - 30 degrees. (Don't forget the 180 degrees = 0
degrees) . Against- the-rule astigmatism is axis 90 degrees + or - 30
degrees. Everything that is left over (30-60 and 120-150) is considered
oblique astigmatism. Of course, axis refers to the degree location of
the cylinder of an astigmatic lens or astigmatic eye. With is generally
more common. Oblique is usually the least common.
Thomas C. Kopan, O.D. - Dana Point, CA
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