Astigmatism

Astigmatism occurs when the cornea (the clear front surface of the eye) or, less commonly, the lens inside the eye, has an irregular curvature rather than a smooth, evenly rounded shape. Instead of focusing light to a single sharp point on the retina, an astigmatic eye focuses light at multiple points, resulting in blurred or distorted vision at all distances. Common symptoms include blurry vision, glare, halos around lights, eye strain, and headaches, especially with prolonged reading or screen use.

There are two distinct categories of astigmatism, and the distinction matters significantly for treatment.

Regular Astigmatism

Regular astigmatism is by far the most common type. In this form, the cornea is shaped more like a football than a basketball — steeper in one direction and flatter in the direction perpendicular to it, but consistently and symmetrically so across the corneal surface. This predictable pattern means the astigmatism can be measured and corrected in a straightforward way, and it typically has genetic origins or develops gradually as a normal variation in eye shape.

Irregular Astigmatism

Irregular astigmatism occurs when the cornea’s surface is asymmetric and doesn’t follow a smooth, predictable pattern — the curvature varies unevenly across different points of the cornea rather than in two consistent, opposite directions. This type is less common and is usually caused by an underlying corneal condition or event, such as:

• Keratoconus, a progressive thinning and bulging of the cornea
• Corneal scarring, from injury, infection, or prior surgery
• Irregular healing after eye surgery, including certain complications of refractive or corneal procedures
• Corneal dystrophies, a group of inherited conditions affecting corneal shape or clarity

Because irregular astigmatism doesn’t follow a uniform pattern, it’s generally harder to correct fully with glasses, and typically requires more specialized treatment approaches.

Treatment Options

The right treatment for astigmatism depends heavily on whether it’s regular or irregular, as well as its severity and whether cataracts or other eye conditions are also present.

1. Glasses

Prescription glasses with cylindrical lens correction are a simple, non-invasive option for regular astigmatism. Many patients achieve clear vision with properly prescribed glasses.

Glasses may be less effective for significant irregular astigmatism because they cannot fully compensate for complex variations in corneal curvature.

2. Soft Toric Contact Lenses

Soft toric contact lenses are designed with different optical powers in different meridians to correct regular astigmatism. They can provide clear vision for patients who prefer contact lenses over glasses.

However, standard soft toric lenses may not adequately correct significant irregular astigmatism.

3. Rigid Gas Permeable (RGP) and Specialty Contact Lenses

Rigid gas permeable (RGP) lenses maintain their shape on the eye and create a more regular optical surface over the cornea. They can improve vision in patients with irregular astigmatism, including some cases associated with keratoconus or corneal scarring.

Depending on the condition and the patient’s needs, other specialty lenses may be considered:

• Hybrid lenses: Combine a rigid central optical zone with a soft outer skirt.
• Scleral lenses: Rest on the white part of the eye and vault over the cornea, creating a fluid-filled space that can help improve vision and comfort.

These specialty lenses may provide better visual correction when glasses or standard soft contact lenses are insufficient.

4. Laser Vision Correction: LASIK and PRK

For appropriately selected patients with regular astigmatism, laser vision correction procedures such as LASIK and PRK reshape the cornea to reduce refractive errors, including astigmatism.

Not everyone is a suitable candidate. A comprehensive evaluation of corneal thickness, corneal shape, prescription stability, and overall eye health is essential.

Patients with significant irregular astigmatism or progressive corneal conditions such as keratoconus generally require additional evaluation. LASIK and PRK may be inappropriate in these cases because removing corneal tissue can compromise an already weakened cornea.

5. Toric Intraocular Lenses (IOLs)

For patients undergoing cataract surgery who also have regular corneal astigmatism, a toric intraocular lens (IOL) may correct both the cataract-related vision problem and some or all of the astigmatism.

Toric IOLs contain different focusing powers in specific directions and must be carefully measured and positioned during surgery. They can reduce dependence on glasses after surgery, although glasses may still be needed for certain activities.

6. Additional Treatments for Irregular Astigmatism

When irregular astigmatism is associated with a progressive corneal condition, treatment may focus on stabilizing the cornea as well as improving vision.

Depending on the diagnosis, options may include:

• Corneal cross-linking: Used in appropriate cases of progressive keratoconus to help strengthen the cornea and slow further progression.
• Corneal transplantation: Considered in selected cases of advanced corneal disease when other treatments do not provide adequate results.
• Specialty contact lenses: Used to improve vision when conventional glasses or contact lenses are insufficient.

The appropriate treatment depends on the underlying cause and the severity of the corneal changes.

How Is Astigmatism Diagnosed?

An accurate diagnosis is the first step toward choosing the right treatment.

During a comprehensive eye examination, your eye doctor may evaluate your prescription, corneal shape, and overall eye health. Corneal topography or tomography may be recommended to map the corneal surface and identify patterns of regular or irregular astigmatism.

These measurements help determine whether glasses, contact lenses, laser vision correction, or cataract surgery with a toric IOL may be appropriate.

Find the Right Astigmatism Treatment for Your Eyes

Astigmatism affects each patient differently. While many cases of regular astigmatism can be corrected effectively with glasses, contact lenses, or laser vision correction, irregular astigmatism may require a more specialized approach.

At New York Eye & Laser, our eye care team evaluates your vision and eye health to help identify suitable treatment options for your individual needs.

If you experience blurry vision, glare, eye strain, or difficulty seeing clearly at different distances, schedule a comprehensive eye examination to discuss your symptoms and correction options.

Medical disclaimer: This article is intended for educational purposes only and does not replace a comprehensive eye examination or individualized medical advice. Eligibility, risks, recovery, and visual outcomes vary by patient.