The short answer: Astigmatism is a very common, harmless difference in the curve of your eye. Instead of being round like a basketball, the front of the eye is shaped a little more like a rugby ball, so light focuses unevenly and vision blurs or stretches at every distance. It is a refractive error, not a disease, and glasses correct it fully with a cylindrical lens.
What astigmatism actually is
A perfectly round cornea focuses light to a single point. With astigmatism, the cornea (or sometimes the lens inside the eye) is curved more in one direction than the other, so light focuses at two points instead of one. The result is blur or a slight stretch and ghosting, at both near and far. Most people have at least a small amount, and it often occurs alongside nearsightedness or farsightedness.
How it feels
Common signs are blurry or smeared vision at all distances, eye strain, squinting, and headaches after focused work. Lights at night, such as headlights and streetlights, may look streaked or haloed. These are also signs of other refractive errors, which is why an eye exam is the way to confirm it.
How glasses correct it
Astigmatism is corrected with a cylindrical lens, which adds extra focusing power in one specific direction to balance the uneven curve. Once the prescription is right, vision is sharp again. Glasses and toric contact lenses both work, and stronger astigmatism is where a well-made lens and correct centering matter most; a good anti-reflective coating also helps with the night-time streaking.
Reading it on your prescription
Astigmatism shows up as two extra numbers on your prescription:
- CYL (cylinder): the amount of astigmatism correction.
- AXIS: the direction, from 1 to 180 degrees, where that correction sits.
If those boxes are filled in, you have astigmatism. Our full guide to reading your prescription explains every line.
When to see an eye doctor
Blurry vision at all distances, new night-time glare, or frequent eye strain are worth an exam. Astigmatism is easily measured and corrected, and a check also rules out other causes. This article is general information, not medical advice; an eye doctor diagnoses and prescribes.
From our test bench. On the product side, astigmatism is where lens centering earns its keep. A cylindrical correction only works when the axis lines up with your eye, so a frame that sits crooked or lenses ground off your PD undo the benefit. We check alignment and centering closely on any prescription with a CYL value.
FAQ
Is astigmatism bad for your eyes?
No. Astigmatism is a common, harmless refractive error, not a disease. It simply means the eye focuses light unevenly, and glasses or contacts correct it fully.
Can glasses fully correct astigmatism?
Yes, in most cases. A cylindrical lens adds focusing power in the direction your eye needs, restoring sharp vision. Strong astigmatism relies on accurate axis and centering to work well.
How do I know if I have astigmatism?
Check your prescription for values in the CYL and AXIS boxes; if they are filled in, you have astigmatism. Blurry vision at all distances and streaky night lights are common signs an exam can confirm.
Part of The Complete Guide to Prescription Lenses · Related: how to read your prescription · Browse eyeglasses · Last updated: August 5, 2026
