What is astigmatism?
Astigmatism is a common eye condition that causes blurred vision. Many people have some degree of astigmatism.
In this condition, some part of your eye — usually the cornea has an irregular curve. The cornea is the outer layer of the eye. It helps your eye focus light so you can see.
What happens to the eye in astigmatism?
Our eyes have a spherical, or round, shape. When light enters the eye, it refracts evenly. Refraction mean light changes direction when it enters your eye at an angle. When light refracts evenly, it focuses precisely on the retina at the back of your eye. You see objects clearly.
If you have astigmatism, your eye’s shape is like a football or the back of a spoon. When light enters the eye, it refracts unevenly — more in one direction than the other. The light can’t properly focus on the retina. When that happens, only one part of the object is in focus at a time. At any distance, things look blurry and wavy. Some people with astigmatism experience eyestrain rather than blur, while others experience both.
The curvature can change, so astigmatism can increase and decrease over time.
What other conditions may occur with astigmatism?
Astigmatism is one of several conditions known as refractive errors, which affect how our eyes refract or bend the light. Other refractive errors include:
Who is at risk for astigmatism?
Factors that may put you at higher risk for astigmatism include:
- Hispanic or Black ethnicity.
- Being nearsighted or farsighted.
- Having a mother who smoked during pregnancy.
How common is astigmatism?
Astigmatism is a common eye condition. About one in three people has some degree of astigmatism. It happens along with nearsightedness or farsightedness.
What are the types of astigmatism?
Corneal astigmatism is the main type. The cornea is egg-shaped instead of round.
Lenticular astigmatism affects the lens, not the cornea. The lens has imperfections that prevent images from reaching the retina clearly. People with this type of astigmatism often have a normal-shaped cornea, though it is possible to have both.
Is astigmatism the same as lazy eye?
These two eye conditions are not the same, but they can go together. Lazy eye, or amblyopia, is a different eye condition where vision in one eye is weaker than in the other. Unbalanced astigmatism — a difference between the two eyes — can cause lazy eye. In childhood, the brain develops a preference for the eye that provides a better image and neglects the other eye, causing vision to get worse in a sometimes permanent way. Unfortunately, lazy eye can occur without patients or their parents noticing. Amblyopia is treatable if caught early, so children should be checked often for vision problems — at least annually.
What causes astigmatism?
Astigmatism is often hereditary, which means it’s passed down from your parents. It can also be the result of eyelids putting pressure on the cornea. It can get better or worse over time.
Sometimes, astigmatism happens after an eye injury or surgery. Another cause is a condition called keratoconus. In this condition, the cornea becomes thinner and more cone-shaped over time. You end up with severe astigmatism. Some people with keratoconus need a corneal transplant.
What are the symptoms of astigmatism?
If you have astigmatism, you may have:
These symptoms are also symptoms of several other conditions. An eye specialist can help diagnose the problem.
It can be tricky to diagnose astigmatism in children. It often goes undetected, because children may not complain about blurred vision. If your child mentions ongoing headaches or eye troubles, talk to your child’s healthcare provider.