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Astigmatism (Lazy Eye)
What It Is
Astigmatism is a refractive error — one of the most common vision conditions — caused by an irregular curvature of the cornea or the lens inside the eye. Instead of being perfectly round like a basketball, the surface is shaped more like a football. This uneven curve prevents light from focusing on a single point on the retina, resulting in blurred or distorted vision at any distance.
It is not a disease. Most people have at least a small amount of astigmatism, and mild cases may not require correction. Larger amounts can cause significant blur, eye strain, headaches, or difficulty with detailed tasks such as reading or night driving.
Astigmatism often occurs alongside myopia (nearsightedness) or hyperopia (farsightedness). Together, these are known as refractive errors — conditions that affect how the eye bends (refracts) light.
Causes
Astigmatism can develop in childhood or adulthood and may be present from birth. Common causes include:
- Natural variations in eye growth: Subtle differences in the shape or alignment of the eye’s structures can create uneven curvature of the cornea or lens.
- Genetics: Astigmatism frequently runs in families.
- Eyelid pressure: Research shows that the pressure of the eyelids on the cornea can influence corneal shape over time.
- Eye injuries or surgery: Scarring or changes to the cornea after injury or surgery may lead to astigmatism.
- Keratoconus and other corneal conditions: In rare cases, a progressive condition such as keratoconus causes the cornea to thin and bulge into a cone shape. This results in high levels of irregular astigmatism that cannot be corrected fully with glasses. These patients often require specialty contact lenses or, in advanced cases, corneal procedures such as cross-linking or transplantation.
Symptoms
Astigmatism can be subtle. Even mild cases can affect the clarity and comfort of vision. Common symptoms include:
- Blurred or distorted vision at any distance
- Difficulty seeing clearly at night
- Eyestrain or visual fatigue
- Headaches during or after visual tasks
- Squinting
- Double vision (in more advanced cases)
Children may not notice symptoms, which makes early eye examinations essential.
How It’s Diagnosed
Astigmatism is identified during a comprehensive eye examination performed by an optometrist. Optometrists can distinguish between corneal astigmatism (caused by irregularity of the cornea) and lenticular astigmatism (from the internal lens). Testing may include:
- Visual acuity testing: Reading standardized letters or symbols to assess clarity.
- Refraction testing: Determining the exact optical prescription needed to focus light accurately.
- Keratometry: Measuring the curvature of the cornea.
- Corneal topography: A detailed computerized map that identifies regular and irregular astigmatism; essential for diagnosing conditions like keratoconus.
- Retinoscopy: A light-based assessment to evaluate how the eye focuses light.
Treatment
Astigmatism is highly treatable. Most cases can be fully corrected with optical or surgical options.
Eyeglasses
The most common and straightforward treatment. Cylindrical lenses precisely counteract uneven curvature to bring light to a single focus point on the retina.
Contact Lenses
Toric contact lenses are specifically designed for astigmatism. They offer a wider field of view and are ideal for people with active lifestyles. Proper fitting by an optometrist is essential for stability and clarity. For irregular or high astigmatism (e.g., keratoconus), specialty lenses such as rigid gas permeable, scleral, or hybrid lenses may be recommended.
Laser Vision Correction
Procedures like LASIK or PRK reshape the cornea to correct astigmatism. They are suitable for adults with stable prescriptions and healthy eyes.
Orthokeratology (Corneal Refractive Therapy)
Specially designed rigid contact lenses worn overnight gently reshape the cornea to provide clear vision during the day without lenses. Most effective for low levels of astigmatism.
Corneal Treatments for Keratoconus
Depending on severity, options may include:
- Corneal cross-linking
- Specialty contact lenses
- Corneal transplant surgery
Your optometrist will determine which option is most appropriate based on the cause and severity of the astigmatism.
When to See an Optometrist
Book an eye exam if you notice:
- Blurred, distorted, or doubled vision
- Frequent headaches or eye fatigue
- Trouble seeing clearly at night
- Changes in how your glasses or contact lenses perform
- Increased glare sensitivity
Children should receive routine eye examinations even if they appear to see well, as they may not report symptoms. Early detection prevents learning challenges linked to uncorrected vision issues.
If symptoms progress rapidly — especially distortion or unexplained blur — an optometrist should assess for conditions such as keratoconus.