What is astigmatism, and how is it corrected?

Astigmatism is one of the most common findings in an eye exam, and one of the most misunderstood. People hear the word and assume something is wrong with their eyes. It is not a disease. It is a shape, and it is very correctable. Here is what it means in plain terms.

The simple explanation

A perfectly shaped cornea, the clear front surface of your eye, is round like a basketball. An eye with astigmatism is shaped more like a rugby ball, curved more in one direction than the other. Because of that uneven curve, light entering the eye focuses at more than one point instead of a single sharp point. The result is blur or distortion at both near and far distances.

Most people have at least a little astigmatism. Small amounts often need no correction at all. Larger amounts are what cause the symptoms below.

Common symptoms

• Blurred or stretched vision at all distances, not only far or only near
• Eye strain and tiredness, especially after reading or screen time
• Headaches after focusing for long periods
• Squinting to sharpen an image
• Streaking or halos around lights at night, such as headlights and street lamps

These signs can point to other things too, which is why an exam matters rather than self-diagnosis.

What causes it

Astigmatism is usually just the natural shape of your eye, often present from birth and sometimes running in families. It frequently appears alongside nearsightedness or farsightedness. It can change slowly over time, which is one reason regular eye tests are worth keeping up. It is not caused by reading in dim light or sitting too close to a screen, common myths worth retiring.

How glasses correct it

Glasses fix astigmatism with a cylindrical lens, a lens ground to bend light more in one direction than the other, cancelling out the eye's uneven curve. On your prescription this shows up as two extra numbers: CYL, the strength of the correction, and AXIS, the angle it needs to sit at. When the lens is made and fitted correctly, the world snaps into a single sharp focus.

How contact lenses correct it

Contact lenses can also correct astigmatism using a design called a toric lens. Toric lenses are weighted so they stay in the right orientation on your eye rather than rotating out of position. They take a slightly more precise fitting than regular lenses, but they work well for many people who prefer contacts. An optometrist confirms whether they suit your eyes.

Will it get worse?

Astigmatism can shift gradually, especially in younger people, and stay fairly stable in adulthood. A sudden or fast change is worth having checked promptly, since it can occasionally point to something that needs attention. For most people, though, it is a stable, manageable part of their prescription that an eye test tracks over time.

The takeaway

Astigmatism is normal, common, and correctable with glasses or contact lenses. The only way to know how much you have, and the exact numbers to correct it, is a proper eye exam that measures the shape of your eye.

Why the lens matters as much as the number

With astigmatism, the angle is everything. The right CYL at the wrong AXIS still feels off, so the lens has to be made to the angle your eye actually needs and hold it there.

Book a Vision7 eye test at your nearest Vision Express store. The seven-step exam measures your cylinder and axis precisely, so your correction is built on the real shape of your eye rather than an estimate.

Then ask for the Shamir Opulens Exact at the counter. It is made to your measurements, so the cylinder and axis are cut precisely and the axis stays where it should. That is what removes the slight pull, tilt or stretched feeling people often report when astigmatism is corrected loosely. If your worst moment is night driving, with streaks off headlights, the Nikon Seemax Infinite Z is the step up for low light.

If you would rather wear contacts, ask about a contact lens fitting in store. Toric lenses only sit correctly when the fitting is measured properly first.

Every pair comes with free lifetime ultrasonic cleaning and free lifetime custom fitting and adjustment, so your frames keep sitting at the angle they were fitted at.