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Astigmatism is a vision problem that causes blurriness, visual distortion, and difficulty seeing at night, among other symptoms.1 Researchers don’t exactly know what causes astigmatism, but they do know that the condition occurs when the cornea (or, the outermost layer of your eye) changes in shape. You may also be at an increased risk of developing astigmatism if you have a family history of the condition, experience an eye injury, or undergo eye surgery.
It’s estimated that 40% of the population will experience this condition at some point in their lifetime.2 Fortunately, there are several treatment options that focus on correcting astigmatism. These include getting glasses, using special contact lenses, or having surgery to fix the shape of the cornea.
Types of Astigmatism
The type of astigmatism you have can help your eye care provider figure out the treatment options that are right for you. There are several types of astigmatism, including:
Corneal: The most common type which occurs when there is a change in the curvature or shape of the cornea
Lenticular: Happens when there is a change in the lens of the eye
Myopic: A type of astigmatism that occurs in people who have nearsighted eyes
Hyperopic: A type of astigmatism that occurs in people who have farsighted eyes
Mixed: Affects people who are farsighted in one eye and nearsighted in the other eye
Symptoms
The most common symptom of astigmatism is changes in your ability to see properly. That said, a variety of other vision-related symptoms may also occur, including:
Blurry vision: Astigmatism affects your ability to see things close by and far away. It’s common to experience blurriness or other vision distortions.
Squinting: This common reaction of partially bringing your eyelids together occurs when your eyes aren’t able to see clearly.
Eye strain: When you can’t see as well, squinting can cause eye strain or fatigue, resulting in your eyes feeling heavy, watery, or burning. As a result of the eye strain, it can also be common to experience headaches.
Trouble seeing in the dark: Astigmatism can sometimes make it difficult for your eyes to adjust to changes in lighting. That said, some people experience trouble seeing at night or in other low-light conditions.
Causes
In eyes without astigmatism, light enters the eye and hits the retina—which is a sensitive layer located at the back of the eye that is responsible for sending information to the optic nerve in your brain. As light enters your eye, your retina triggers nerve impulses to your brain. When your optic nerve becomes triggered, your brain is able to process a visual image for your eyes to see.
However, when you have astigmatism, your retina isn’t able to function properly, which can affect your vision. The reason this happens is because astigmatism causes your eyes to change shape. As a result, you aren’t able to properly focus on the objects in front of you, which can make your vision seem blurry or distorted.4
Why exactly astigmatism happens is currently unknown. Some researchers theorize that normal changes in vision as you age or having an underlying eye condition can all increase your risk of developing astigmatism.3
Risk Factors
Anyone can develop astigmatism, but some factors may increase your likelihood of experiencing symptoms of the condition. These risk factors include:
Having a family history of astigmatism
Experiencing an injury to the eye
Undergoing eye surgery or having complications after the procedure
Diagnosis
If you notice changes to your vision, it’s good practice to see your eye care provider (such as an optometrist or ophthalmologist) for testing. During your eye exam, your provider can learn more about your symptoms, check your vision, and rule out other conditions that may be causing blurriness or eye strain.
Your provider can perform a number of diagnostic tests to learn more about your condition and test for other eye conditions (such as nearsightedness or farsightedness). These tests include:4
Visual acuity: Tests how well you see objects close by and far away by reading letters of different sizes on a chart
Refraction: Assesses how much refractive error (lack of focus in the eyes) you have
Retinoscopy: Uses a handheld device called a retinoscope to test the level of refractive error in your eye
Keratometry: Involves using a device known as a keratometer to measure the curvature and shape of the cornea
Pachymetry: Measures the thickness of the cornea while using a device called a pachymeter to determine if you need eye surgery
Treatment
Depending on the severity of your condition, there are a variety of treatment options that your eye care provider can consider. The goal of astigmatism treatment is to correct the underlying cause of your symptoms or reduce the intensity of your symptoms.
Mild cases of astigmatism may not always require treatment, but will often need regular check-ups to assess the progress of your condition. More severe astigmatism cases may involve treatment options such as glasses, corrective lenses, or surgery.