Here’s the deal: Bossy’s daughter has a congenital eye anomaly, which means her visits to the Ophthalmologist occur with the kind of frequency she knows all about those extraneous Hs and Ls in the word Ophthalmologist, which has nothing to do with this post — welcome to Bossy’s scrambled
Fast forward to yesterday at the eye doctor’s office, when Bossy’s daughter was fitted for contact lenses. Like many of us, where us equals Bossy and the other people who don’t know if it’s fitted for lenses or fit, Bossy’s daughter has an astigmatism.
“What’s an astigmatism?” Bossy’s daughter asked Bossy the eye expert last night. Bossy, by the way, who has shared this diagnosis her whole life, but was never sure if it was astigmatism or a stigmatism.
So Bossy decided to research this condition for her daughter, utilizing only the most reputable medical sources, which means Bossy looked it up on Wikipedia. And here is what she learned:
Astigmatism refers to the image-formation property of an optical system which focuses a single point source in object space into a single point in image space.
Why didn’t you say so — that explains everything! But it gets worse:
Astigmatism is applicable only in the approximation provided by geometric optics. In reality, image formation is at best diffraction limited and point-like images are not possible.
Image, point, object, space, diffraction. Bossy doesn’t know about her very wise council, but after a morning invested in Wikipedia, this is what Bossy got out of it:
So Bossy decided to take a closer look at astigmatism — and see how Bossy did that? Made a visual pun right here in the middle of her eye tutorial?
The first thing Bossy discovered is that astigmatism most often refers to an irregular curvature of the eye’s cornea:
The cornea acts as the transparent window over the part of your eye that has its color, and it is here where most of the focusing power of the eye occurs, as it bends and focuses light onto the retina in the back of the eye:
When the cornea has an irregular curvature, as in the case with an astigmatism, the cornea still bends light, but it focuses the image onto the retina at two different points. It’s this discrepancy between the two refracted planes which result in blurriness:
The amount of blurriness and the ability to correct for it with standard eyeglasses or contact lenses has to do with how many diopters big the astigmatism is: