Imperfect curvature of your eye can cause blurred distance and near vision. Learn about this common and treatable eye condition.
Astigmatism (uh-STIG-muh-tiz-um) is a common and generally treatable imperfection in the curvature of the eye that causes blurred distance and near vision.
Astigmatism occurs when either the front surface of the eye (cornea) or the lens inside the eye has mismatched curves. Instead of having one curve like a round ball, the surface is egg-shaped. This causes blurred vision at all distances.
Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness. Often it's not pronounced enough to require corrective action. When it is, treatment options are corrective lenses or surgery.
Signs and symptoms of astigmatism may include:
See an eye doctor if your eye symptoms detract from your enjoyment of activities or interfere with your ability to perform everyday tasks. An eye doctor can determine whether you have astigmatism and, if so, to what degree. He or she can then advise you of your options to correct your vision.
Children may not realize their vision is blurry, so they need to be screened for eye disease and have their vision tested by a pediatrician, an ophthalmologist, an optometrist or another trained screener at the following ages and intervals.
The eye has two structures with curved surfaces that bend (refract) light onto the retina, which makes the images:
In a perfectly shaped eye, each of these elements has a round curvature, like the surface of a smooth ball. A cornea or lens with such curvature bends (refracts) all incoming light equally to make a sharply focused image directly on the retina at the back of the eye.
If either the cornea or the lens is egg-shaped with two mismatched curves, light rays aren't bent the same, which means that two different images form. These two images overlap or combine and result in blurred vision. Astigmatism is a type of refractive error.
Astigmatism occurs when the cornea or lens is curved more steeply in one direction than in another. You have corneal astigmatism if your cornea has mismatched curves. You have lenticular astigmatism if your lens has mismatched curves.
Either type of astigmatism can cause blurred vision. Blurred vision may occur more in one direction: horizontally, vertically or diagonally.
Astigmatism may be present from birth, or it may develop after an eye injury, disease or surgery. Astigmatism isn't caused or made worse by reading in poor light, sitting too close to the television or squinting.
Astigmatism may occur in combination with other refractive errors, which include:
Astigmatism is diagnosed with an eye exam. A complete eye exam involves both a series of tests to check eye health and a refraction, which determines how the eyes bend light. Your eye doctor may use various instruments, aim bright lights directly at your eyes and ask you to look through several lenses. Your doctor uses these tests to examine different aspects of your eyes and vision and to determine the prescription needed to provide clear vision with eyeglasses or contact lenses.
The goal of treating astigmatism is to improve vision clarity and eye comfort. Treatments are corrective lenses or refractive surgery.
Wearing corrective lenses treats astigmatism by counteracting uneven curvatures of your cornea or lens.
Types of corrective lenses include:
Contact lenses. Like eyeglasses, contact lenses can correct most astigmatism. They are available in a variety of types and styles.
Contact lenses are also used in a procedure called orthokeratology. In orthokeratology, rigid contact lenses are worn during the night while sleeping until the curvature of the eye evens out. Then the lenses are worn less frequently to maintain the new shape. If treatment is discontinued, the eye returns to its former shape and refractive error.
Wearing contact lenses for extended periods of time increases the risk of infection in the eye.
Ask your eye doctor about the pros and cons and risks of contact lenses and what might be best for you.
Refractive surgery improves vision and reduces the need for eyeglasses or contact lenses. An eye surgeon uses a laser beam to reshape the curves of the cornea, which corrects the refractive error. Before surgery, doctors will evaluate you and determine if you're a candidate for refractive surgery.
Types of refractive surgery for astigmatism include:
Other types of refractive surgeries include clear lens extraction and implantable contact lenses. There is no one best method for refractive surgery, and you should make a decision only after a complete evaluation and thorough discussion with your surgeon.
Some of the possible complications that can occur after refractive surgery include:
Discuss the potential risks and benefits of these procedures with your eye doctor.
You may encounter three kinds of specialists as you seek help for various eye conditions:
No matter which type of eye specialist you choose, here's some information to help you get ready for your appointment.
Preparing a list of questions will help you make the most of your visit. For astigmatism, some basic questions to ask include:
Your doctor may ask:
October 5th, 2021