Astigmatism

Astigmatism is a common refractive error caused by an irregularly shaped cornea or lens. Instead of being round like a basketball, the eye is shaped more like a football, causing light to focus at multiple points rather than one. This results in blurred or distorted vision at all distances.

How Astigmatism Works

Normal Eye vs. Astigmatism

Normal eye (spherical):

• Cornea is evenly curved like a basketball
• Light focuses at a single point on the retina
• Clear image forms

Astigmatic eye (toric):

• Cornea or lens has uneven curvature (like a football)
• Light focuses at multiple points
• Image is blurred or distorted

Types of Astigmatism

Regular Astigmatism (Most Common)

• The two main curvatures (meridians) are perpendicular
• Easily corrected with glasses or standard toric contacts

Irregular Astigmatism

• Curvatures are not perpendicular or vary across cornea
• Causes: keratoconus, corneal scarring, trauma
• May need rigid contacts or specialty lenses

Symptoms

Vision Symptoms

• Blurred vision at all distances
• Distorted or stretched images
• Difficulty seeing fine details
• Problems with night vision
• Halos or glare around lights
• Squinting to see clearly

Strain-Related Symptoms

• Eye strain and fatigue
• Headaches
• Difficulty with prolonged reading or screen use
• Eye discomfort

In Children

• Squinting or tilting head
• Sitting close to TV or holding books close
• Difficulty in school (can't see board clearly)
• Eye rubbing
• May not complain (don't know vision should be clearer)

Causes

Corneal Astigmatism (Most Common)

• Irregular corneal curvature
• Often present from birth
• Hereditary component
• May change slightly over time

Lenticular Astigmatism

• Irregular lens shape inside the eye
• Less common than corneal
• May change with cataract development

Acquired Causes

• Keratoconus—progressive corneal thinning
• Corneal scarring from injury or infection
• Previous eye surgery
• Pterygium (growth on cornea)
• Eyelid masses pressing on cornea

Diagnosis

Eye Examination

• Visual acuity testing—reading the eye chart
• Refraction—determining the prescription
• Keratometry—measuring corneal curvature
• Corneal topography—detailed corneal mapping

Understanding the Prescription

An astigmatism prescription has three parts:

1. Sphere—myopia (-) or hyperopia (+) correction
2. Cylinder—amount of astigmatism
3. Axis—orientation of astigmatism (1-180 degrees)

Example: -2.00 -1.50 x 90

• -2.00 = myopia
• -1.50 = astigmatism amount
• 90 = axis orientation

Treatment Options

Wondering whether glasses or contacts are a better fit? Our glasses and contacts guide walks through the decision.

Glasses

• Most common and straightforward correction
• Cylindrical lens component corrects astigmatism
• Work well for regular astigmatism
• May notice distortion at edges of lens (especially high prescriptions)

Contact Lenses

Toric Soft Lenses

• Designed to stay oriented correctly on eye
• Available in daily, bi-weekly, and monthly options
• Work well for most regular astigmatism

Rigid Gas Permeable (RGP) Lenses

• Create a new smooth optical surface
• May provide sharper vision
• Good for irregular astigmatism
• Require adaptation period

Hybrid Lenses

• Rigid center with soft skirt
• Comfort of soft lens with optics of rigid lens

Scleral Lenses

• Large diameter lenses that vault over cornea
• Excellent for irregular astigmatism
• Very comfortable once adapted

Refractive Surgery

For stable adult astigmatism:

LASIK

• Reshapes cornea with laser
• Can correct moderate astigmatism
• Quick recovery

PRK

• Surface laser treatment
• Alternative to LASIK
• Longer healing but good results

SMILE

• Newer procedure
• Less corneal surface disruption

Astigmatic Keratotomy (AK)

• Incisions to flatten steep meridian
• Often combined with cataract surgery

Toric IOLs

• Astigmatism-correcting lens implants
• Placed during cataract surgery
• Corrects astigmatism while treating cataract

Special Situations

Astigmatism with Keratoconus

Keratoconus causes progressive irregular astigmatism:

• Glasses may not correct adequately
• Rigid or scleral contacts often needed
• Corneal cross-linking may slow progression
• Severe cases may need corneal transplant

Astigmatism After Cataract Surgery

Some astigmatism may remain or change after surgery:

• May need glasses for residual astigmatism
• Limbal relaxing incisions (LRI) can reduce it
• Laser enhancement possible in some cases
• Toric IOL exchange rarely needed

Childhood Astigmatism

Important to detect and treat:

• Can cause amblyopia if significant and uncorrected
• May need full-time glasses wear
• Regular monitoring as eyes develop
• Usually stable but can change during growth

When to See a Doctor

Frequently Asked Questions

Is astigmatism serious?

Most astigmatism is not serious—it's a common optical imperfection easily corrected with glasses or contacts. However, progressive irregular astigmatism (like keratoconus) requires monitoring and specialized treatment.

Can astigmatism get worse?

Minor changes are normal over time. Significant worsening, especially if rapid or irregular, may indicate conditions like keratoconus and should be evaluated.

Can astigmatism be cured?

Astigmatism can be corrected but not "cured." Refractive surgery can permanently reshape the cornea to reduce or eliminate astigmatism, though it may regress slightly over time.

Why do my glasses seem distorted at the edges?

Higher astigmatism corrections in glasses can cause peripheral distortion. This is normal. It may be reduced with certain lens designs (aspherical lenses) or by switching to contacts.

Can I wear regular contacts with astigmatism?

Mild astigmatism may be adequately corrected with spherical soft contacts. Moderate to higher astigmatism usually needs toric (astigmatism-correcting) lenses for clear vision.

Is astigmatism hereditary?

Yes, there's a hereditary component. If parents have astigmatism, children are more likely to develop it. However, environmental factors also play a role.

References