Astigmatism Causes Correctable Blurred Vision
Q. I wear corrective glasses for astigmatism, but I don't really understand what astigmatism is.
A. Astigmatism means that the cornea of the eye has an irregular shape. The cornea is the clear covering over the lens and the iris. The iris controls how much light enters the eye. The lens focuses the light on the retina, the light-sensitive area at the rear of the eye. The cornea protects these structures and helps to transmit light through the eye.
The cornea is normally round, but in people with astigmatism, it may be an oval. As a result, light scatters as it passes through the cornea; the light rays do not focus on a single point on the retina. That focus is what you need for clear vision, just like a camera.
The result of uncorrected astigmatism is blurred vision. The image is distorted, regardless of whether you're looking at something distant or something close. In this respect, astigmatism is different from nearsightedness, where things in the distance are blurry but not things that are close. It's also different from presbyopia, the condition that causes most of us to need reading glasses. (I've put an illustration on my website, .)
Some people describe the blurred vision as double vision but in only one eye. Astigmatism can lead to eyestrain, squinting and headaches from working to focus on near or distant objects.
People are born with astigmatism, but it may not be apparent until a child begins to attend school or learns to read. …