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Overview
What Is Astigmatism?
Astigmatism is a common refractive error caused by an uneven curve in the cornea or lens. Instead of focusing light evenly on the retina, the eye may produce blurred or distorted vision at near, far, or multiple distances. This astigmatism definition describes a focusing problem, not an infection or disease. It may occur alone or along with nearsightedness or farsightedness.
| Vision pattern | How light focuses | What a person may notice |
|---|---|---|
| Typical eye | Light focuses more evenly on the retina | Clearer images |
| Astigmatism | Light focuses unevenly or at more than one point | Blurred, stretched, or distorted images |
Symptoms
Astigmatism Symptoms
- Blurred vision (reduced sharpness of vision).
- Distorted vision.
- Eye strain.
- Headaches.
- Squinting to see clearly.
- Difficulty seeing clearly at night.
- Halos or glare around lights.
- Frequent changes in visual clarity.
Causes
What Causes Astigmatism?
Astigmatism occurs when the cornea or lens has an uneven curve instead of a uniformly round shape. This irregular shape causes light to focus unevenly, or at more than one point, on the retina.
- A cornea that is shaped more like an oval than a round ball.
- An irregularly shaped lens inside the eye.
- Changes in the cornea after an eye injury or eye surgery.
- Certain corneal conditions, such as keratoconus, which can progressively change corneal shape.
- Astigmatism present from childhood or inherited within a family.
Risk Factors
Astigmatism Risk Factors
- Family history of astigmatism or other refractive errors.
- Astigmatism during childhood.
- A history of corneal disease or abnormal corneal shape.
- Previous eye injury or eye surgery.
- Having another refractive error, such as nearsightedness or farsightedness.
Complications
Astigmatism Complications
- Persistent eye strain or headaches can interfere with reading, work, or school activities.
- Uncorrected astigmatism in a child can contribute to amblyopia (reduced visual development in one eye or both eyes).
- Blurred vision can affect driving, sports, balance, or other activities that require clear vision.
- An underlying corneal condition may continue to change the shape of the cornea and require specialist care.
For families
Children may not notice a vision problem
Routine eye care is especially important for children because vision development can be affected before they recognize or report blurred vision. Timely correction and follow-up can support normal visual development.
Diagnosis
How Astigmatism Is Diagnosed
An optometrist or ophthalmologist diagnoses astigmatism during a comprehensive eye examination. The clinician reviews symptoms and medical history, checks visual acuity, and measures how the eye focuses light to determine the prescription needed for clear vision.
- Visual acuity testing measures how clearly each eye sees letters or symbols at a distance.
- Refraction testing compares lenses to determine the prescription that provides the clearest vision.
- Keratometry measures the curvature of the cornea.
- Corneal topography maps the cornea’s surface when a more detailed shape assessment is needed.
- A slit-lamp examination checks the cornea, lens, and other structures at the front of the eye.
Treatment & Management
Astigmatism Treatment and Management
COMMON OPTION
Eyeglasses: Prescription lenses are often the simplest and safest correction.
SPECIALTY LENSES
Contact lenses: Toric or other specialty lenses can correct astigmatism when properly fitted and cared for.
SELECTED ADULTS
Refractive surgery: Selected adults may be evaluated for laser or other procedures after a detailed eye assessment.
An astigmatism prescription may include a cylinder power and axis to correct the direction and amount of uneven focusing. Children need age-appropriate correction and follow-up, while contact lens users must follow hygiene instructions and attend scheduled examinations. Glasses for astigmatism and contacts for astigmatism should be prescribed and fitted by an eye-care professional.
Outlook and Prognosis
Astigmatism Outlook and Prognosis
Astigmatism is usually manageable rather than curable with exercises. Glasses or contact lenses commonly provide clear vision, although some prescriptions change with age or eye development.
- Most people achieve useful or clear vision with an accurate prescription.
- Regular eye examinations help identify prescription changes and other eye conditions.
- Children may need closer follow-up to support normal visual development.
- A rapidly changing or unusually irregular prescription may require evaluation for an underlying corneal condition.
When Should You See a Doctor
When Should You See a Doctor for Astigmatism?
- Schedule an eye examination if blurred or distorted vision persists or interferes with daily activities.
- Arrange an evaluation for recurring headaches, eye strain, squinting, or difficulty seeing at night.
- Have a child assessed if they sit unusually close to screens or books, avoid reading, or have difficulty seeing at school or during sports.
- Follow up if glasses or contact lenses no longer provide clear or comfortable vision.
Seek urgent care
Sudden changes are not typical astigmatism
Seek urgent eye assessment for sudden vision loss, severe eye pain, a sudden shower of floaters or flashes, a curtain-like shadow, or sudden marked distortion. These symptoms may indicate a different urgent eye problem.
Branches
1 topic
Astigmatism
Ophthalmology
