Astigmatism: Causes, Symptoms and What an Eye Exam Checks

 Astigmatism is one of the most common refractive errors of the eye, affecting millions of people worldwide. It occurs when the cornea or lens of the eye is irregularly shaped, leading to blurred or distorted vision. This article will explore the causes of astigmatism, its symptoms, and the various treatment options available to help you improve your vision.

What is Astigmatism?

Astigmatism is a refractive error, like nearsightedness (myopia) and farsightedness (hyperopia). It happens when the cornea, the clear outer layer of the eye, or the lens inside the eye is not perfectly round. Instead of having a symmetrical shape like a basketball, the cornea or lens has an asymmetrical, football-like shape, which causes light entering the eye to be focused on multiple points rather than a single point on the retina. This leads to blurry or distorted vision, especially at certain distances.

Causes of Astigmatism

The exact cause of astigmatism is not always known, but several factors contribute to the condition:

  1. Genetics: Family history can contribute, but the exact cause is not always clear. If your parents have astigmatism, you are more likely to have it as well.

  2. Irregular Corneal Shape: Astigmatism often occurs due to an irregularly shaped cornea. Normally, the cornea is round, but in people with astigmatism, it may be more oval or asymmetrical.

  3. Lens Shape: The lens inside the eye can also be a source of astigmatism if it is irregularly shaped. This is known as lenticular astigmatism and may occur due to genetic factors or eye injuries.

  4. Eye Injury or Surgery: Trauma or surgical procedures, such as cataract surgery, can sometimes result in changes to the shape of the cornea or lens, causing astigmatism.

  5. Keratoconus: This is a progressive eye condition where the cornea becomes thinner and more cone-shaped. It can worsen astigmatism over time.

  6. Age-Related Changes: As people age, their eye structures can change, potentially contributing to astigmatism.

Symptoms of Astigmatism

Astigmatism can be mild, moderate, or severe, and the symptoms may vary depending on the degree of the refractive error. Common symptoms of astigmatism include:

  • Blurred or distorted vision: Both near and distant objects may appear blurry or out of focus.

  • Eye strain: You may feel fatigued or experience discomfort after reading, using a computer, or other tasks requiring focus.

  • Headaches: Astigmatism can cause headaches, especially after prolonged visual tasks.

  • Squinting: In an attempt to see more clearly, individuals with astigmatism may squint frequently.

  • Double vision: Astigmatism may cause a shadow or ghost image in one eye. New double vision, especially with both eyes open, should not automatically be attributed to astigmatism; seek prompt medical assessment.

How Astigmatism is Diagnosed

If you notice symptoms like blurred vision, eye strain, or headaches, it is important to schedule an eye exam with an optometrist or ophthalmologist. During the exam, your eye care professional will perform a comprehensive eye test, which may include:

  • Visual acuity test: To measure how well you can see at different distances.

  • Keratometry: To measure the curvature of your cornea and check for irregularities.

  • Refraction test: To determine the type and extent of refractive errors, including astigmatism.

  • Corneal topography: This advanced test maps the surface of the cornea to detect astigmatism and other irregularities.

Treatment Options for Astigmatism

Glasses and contact lenses correct how light focuses without removing the underlying refractive error. Surgery can alter corneal shape in suitable patients, but does not guarantee lifelong freedom from glasses. The most common treatments for astigmatism include:

1. Eyeglasses

Eyeglasses are the most common and simplest way to correct astigmatism. Special lenses called cylindrical lenses are used to compensate for the irregular shape of the cornea or lens, allowing light to focus properly on the retina. The prescription will be tailored to the specific type and degree of astigmatism, helping you achieve clear vision.

2. Contact Lenses

Contact lenses are another option for people with astigmatism. They work similarly to eyeglasses by altering the way light enters the eye. There are several types of contact lenses that may be suitable for astigmatism:

  • Toric lenses: These specialized lenses are designed to address astigmatism by providing different optical power in different meridians of the lens.

  • Rigid gas permeable (RGP) lenses: These hard lenses can provide clearer vision for people with more severe astigmatism.

  • Scleral lenses: These are larger, gas-permeable lenses that rest on the sclera (the white part of the eye) and create a smooth surface over the irregular cornea.

3. Refractive Surgery

LASIK, PRK and other procedures may reduce astigmatism in selected adults. Eligibility depends on stable refraction, corneal shape and thickness, eye health and the procedure’s approved treatment range. A thin or abnormal cornea is not automatically safe for a different laser operation. Discuss dry eye, glare, halos, residual prescription and uncommon serious complications with the surgeon. An implantable toric lens is an intraocular operation with its own eligibility requirements and risks.

4. Orthokeratology

Specially fitted overnight lenses temporarily reshape the cornea in selected eyes. They are not suitable for every amount or type of astigmatism. The effect needs ongoing wear and follow-up, and overnight lens wear carries a risk of corneal infection.

Comfort and Eye Health: What Habits Cannot Do

Screen breaks, suitable lighting and a balanced diet support comfort or general health; they do not reverse cylindrical power or reliably prevent astigmatism. Keep these measures separate from optical correction:

  • Regular eye exams: Routine eye exams are essential for detecting astigmatism early and ensuring the best treatment options.

  • Take breaks from screen time: Prolonged screen use can cause eye strain, so practice the 20-20-20 rule (take a 20-second break every 20 minutes by looking at something 20 feet away).

  • Wear sunglasses: Protect your eyes from UV rays by wearing sunglasses with proper UV protection.

  • Healthy diet: Eating a balanced diet rich in vitamins A, C, and E, as well as omega-3 fatty acids, can help promote eye health.

What to bring to an examination

Bring your current glasses and previous prescription. Describe whether the blur is near, far, constant or intermittent, and whether one eye is worse. These observations help the examiner compare symptoms with measured refraction; they do not establish the diagnosis.

Next: when astigmatism needs correction and how astigmatism correction options differ.

Sources and review

Reviewed October 27, 2026. Educational information; individual diagnosis and treatment require an eye examination.