What is Astigmatism?
Astigmatism is a common vision problem caused by an imperfection in the curvature of your eye’s cornea or lens. With astigmatism, your vision is blurry at all distances.
Normally, the cornea and lens are smooth and curved equally in all directions to help focus light rays onto the retina at the back of the eye. If your cornea or lens isn’t smooth and evenly curved, light rays aren’t refracted or bent properly. This is called a refractive error.
When your cornea has a distorted shape, you have a corneal astigmatism, whereas, when the shape of your lens is distorted, you have lenticular astigmatism. In either case, your vision for both near and far objects is blurry or distorted. A person can have astigmatism along with other refractive errors, such as myopia (nearsightedness) or hyperopia (farsightedness). While adults with significant astigmatism may realize their vision isn’t as good as it should be, children with astigmatism symptoms may not be aware of their condition.
Astigmatisms are sometimes described as regular or irregular. A regular astigmatism occurs when the eye isn’t completely curved like a basketball, but rather shaped like a football. Irregular astigmatism is less common and also occurs when the eye is not completely round and also has uneven curvature.
What is the Main Cause of Astigmatism?
It is not known what causes astigmatism, but genetics is considered a big factor and is often present at birth. Astigmatism can also develop later in life and may result from eye disease, an eye injury or surgery. While reading in low light or sitting too close to the TV screen can irritate your eyes over time or make it harder for your eyes to focus, it is not known to cause astigmatism.
What Are Symptoms of Astigmatism?
Astigmatism symptoms may include the following:
- Blurry vision or areas of distorted vision
- Difficulty seeing at night
- Squinting for clarity
- Eye discomfort
While you might be experiencing one or more of these symptoms, it may not necessarily mean you have astigmatism. You should visit your ophthalmologist for a complete eye exam to determine the causes of your symptoms.
How is Astigmatism Diagnosed?
There are several tests that your ophthalmologist or optometrist might use during a comprehensive exam to diagnose astigmatism, including the following:
- Visual Acuity Assessment Test: Your doctor will ask you to read a chart at a specific distance to determine which line you can read.
- Refraction Test: Your doctor will use a machine called an optical refractor with multiple corrective glass lenses of different strengths. You will be asked to read a chart on the wall while looking through the lenses at different strengths to find the lens that appropriately corrects your vision.
- Keratometry: Your doctor will use a keratometer to measure the curvature of your cornea.
Can Astigmatism Be Treated?
- Mild to moderate astigmatism can usually be corrected with eyeglasses or contact lenses—both can compensate for uneven curves in your cornea and lens. This is the least invasive treatment for astigmatism.
- Orthokeratology (Ortho-K) is a treatment that uses rigid contact lens to temporarily correct the irregular curvature of your cornea.
- Refractive Surgery, such as LASIK, to permanently reshape your cornea.
Your ophthalmologist can determine the best options based on your comprehensive eye exam.
For more details, visit the American Academy of Ophthalmology website.