![]() ![]() ![]() Astigmatism also degrades the image quality of whatever it is you’re looking at, but in a slightly different way. I’ve even corrected up to 8 diopters of astigmatism with the laser, which is really unusual, but potentially treatable. Modern laser vision correction has been correcting astigmatism since 1998. If I cut a tennis ball in half, then squeezed the sides together, it would create the same shape as astigmatism. ![]() What’s astigmatism got to do with it?Īstigmatism, also called cylinder, occurs when the shape of your cornea (the clear dome of collagen over the colored part of your eyes) is not perfectly spherical. So it’s a huge difference in glasses thickness between -4 and -10, but only 6 inches of additional clear vision. If you’re -10, then your vision starts to blur at 1/10th of a meter, 10cm, or about 4 inches away from your face. What this means is that without your glasses on, your vision will start to blur at about 10 inches away from your eyes. So if your contacts are -4 Diopters, then -4=1/f and f=0.25 meters, which is 25 cm, or about 10 inches. As eye doctors, we’re not too concerned with your uncorrected vision, but more concerned with your best-corrected vision, and with your refractive error, which we measure in units called “diopters.” For the very interested (geeks/nerds-hey, I’m one also!) out there, a diopter is D=1/f, where f=the focal length in meters. ![]()
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