Astigmatism: what it is, the signs, and how glasses correct it

Astigmatism is a common focusing problem, not a disease. The clear front of the eye (the cornea), or the lens inside it, is shaped more like a rugby ball than a football. Light then can't come to one sharp point at the back of the eye, so things look blurred, stretched or slightly doubled — up close and far away.

It often comes together with short-sightedness or long-sightedness. Many people are born with some astigmatism, and it can change slowly over the years.

• Blurred or stretched vision at any distance
• Streetlights and headlights with streaks, halos or starbursts at night
• Squinting to see clearly
• Tired eyes or headaches after reading or screen work
• Trouble seeing fine detail, like small print or road signs

Mild astigmatism often goes unnoticed: the eyes keep working to sharpen the picture, which is one reason they feel tired by the end of the day.

An eye test measures how each eye focuses light, and whether that focus differs from one direction to another. On a prescription, astigmatism appears as a cylinder power (CYL) and an axis — the direction it runs, written as a number from 1 to 180.

At My Vision the eye test is free, with no obligation to buy.

Glasses are the most common way to correct astigmatism: the lenses are made to your cylinder power and axis, so light comes back to a single sharp focus. Contact lenses made for astigmatism, called toric lenses, are another option. Your optometrist can explain which suits your eyes and your day.

New glasses for astigmatism can feel strange for a day or two — the floor may look slightly tilted. This usually settles quickly; if it doesn't, the fit or the prescription should be checked.

• Reading in dim light doesn't cause astigmatism.
• Wearing your glasses won't make it worse.
• Squinting doesn't fix it — it only helps for a moment.