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Medical Forum / General / Vision / December 2006Angle of astigmatism - does it make a difference?
I read that dependent on the angle of the astigmatism the same amount can be worse in two people. Which is the worst angle? I've had -0.50 at either 140 or 150 for the last 5 years and this eye is more difficult to correct than the other, could that be the reason? > I read that dependent on the angle of the astigmatism the same amount > can be worse in two people. Which is the worst angle? I've had > -0.50 at either 140 or 150 for the last 5 years and this eye is more > difficult to correct than the other, could that be the reason? Not a doctor, but I think maybe what is being said is that 0/180 astigmatism seems to be subjectively more tolerable to people compared to 90 degree astigmatism. Up/down blur is probably easier to read through compared to left/right blur. I think it's also true that a person can "squint through" 0/180 astigmatism to some extent and you can't with 90. 140 is getting pretty close to half-way between those cases. -- > I read that dependent on the angle of the astigmatism the same amount can be > worse in two people. Which is the worst angle? I've had -0.50 at either 140 > or 150 for the last 5 years and this eye is more difficult to correct than > the other, could that be the reason? Not likely, although "difficult to correct" doesn't really tell us much about your issue. Astig (minus) axis 90 generally produces more noticeable blur than 180. .50 is fairly small. If it associated with hyperopia, that may be a vision issue. If combined with a moderate amount of myopia, then perhaps a miniscule effect. You have oblique angle astigmatism. If you have the same in the opposite direction in the other eye, uncorrected, the combined effect is close to zero. If only in one eye with no other optical correction in either eye, then a potential issue with using spectacle correction comfortably. Conclusion here: there's not enough subjective information or optical data to have a meaningful discussion specific to you. But to answer the subject of your post: Yes! LB, O.D. Astigmatism that uses minus cyl to correct (what optometrist's write their Rx in) in the 180 meridian, or near 180, is more tolerable than any others. Second would be in the 90 meridian, or near. Lastly would be oblique astigmatism, like you have, between 30-60, and between 150-120. The rationalle for this is the types of distortion you get from each lens, and what people are viewing the most, letters or typed print. The cyl in the 180 stretches the letters in the vertical direction, while cyl in the 90 stretches letters in the horizontal direction, both easier to adapt to than having the letters stretched to some oblique angle. Since most of our language has several vertically biased letters like "l", "t", "h", and others the distortions don't change the way the letters look very much, having a shorter adaptation time than obliquely oriented cyl correction. > > I read that dependent on the angle of the astigmatism the same amount can be > > worse in two people. Which is the worst angle? I've had -0.50 at either 140 [quoted text clipped - 18 lines] > > LB, O.D. |
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