What is the treatment for astigmatism (a refractive error)?

Treatment of Astigmatism

Eyeglasses with full cylindrical correction are the first-line treatment for astigmatism, followed by toric contact lenses for those requiring alternatives, and refractive surgery (PRK, LASIK, or SMILE) for patients seeking permanent correction. 1

Non-Surgical Correction

Eyeglasses (First-Line Treatment)

• Eyeglasses should be prescribed before considering contact lenses or refractive surgery for both with-the-rule and against-the-rule astigmatism 1
• Full cylindrical correction effectively treats astigmatism, though adults with previously uncorrected astigmatism may require gradual correction to improve tolerance 2, 1
• Adults with previously uncorrected or partially corrected astigmatism poorly tolerate substantial changes in axis or power, so initial partial correction followed by gradual increases is better accepted 2, 1
• High-index lenses reduce thickness and weight for higher refractive errors, improving comfort and cosmetic appearance 1

Contact Lenses (Second-Line)

For Low to Moderate Astigmatism (<3.00 D):

• Soft toric contact lenses or rigid gas-permeable (RGP) contact lenses effectively correct low to moderate astigmatism 2, 1
• Custom-designed soft toric lenses provide good centration, flexible wear schedules, and improved comfort 2, 1

For High Astigmatism (≥3.00 D):

• Rigid gas-permeable and hybrid contact lenses are highly effective 2, 1
• Bitoric or back-surface toric contact lens designs minimize corneal bearing and improve centration for greater amounts of corneal astigmatism 2, 1
• RGP scleral lenses (diameter >17mm) are excellent options for high and/or irregular astigmatism, particularly with anisometropia 2, 1

Surgical Correction

Photorefractive Keratectomy (PRK)

• PRK involves removing the central corneal epithelium and using excimer laser to ablate Bowman layer and superficial corneal stroma 3
• Axis alignment is crucial in treating astigmatic errors because misalignment significantly reduces treatment effectiveness 3, 1
• Reference marks should be placed on the operative eye while the patient is seated upright before the laser procedure to compensate for ocular cyclotorsion 3, 1
• Mitomycin-C (0.02% for approximately 15 seconds) is often used off-label to reduce corneal subepithelial haze, particularly with high corrections 3

LASIK (Laser-Assisted In Situ Keratomileusis)

• LASIK procedures for astigmatism include PRK variants (LASEK, epi-LASIK), LASIK, SMILE, and astigmatic keratotomy (AK) 3
• Wavefront-guided, wavefront-optimized, and topography-guided patterns are available to reduce higher-order aberrations 3
• Wavefront-guided or wavefront-optimized techniques maintain a more prolate corneal shape, reducing induced spherical aberration and may improve quality of vision under dim lighting conditions 3
• Iris registration or tracking systems help maximize accuracy of the astigmatic ablation axis 3

Small Incision Lenticule Extraction (SMILE)

• Keratorefractive lenticule extraction (KLEx) corrects astigmatism ranging from 0.25 D to 5.00 D 1
• Cyclotorsion compensation significantly improves outcomes and results in lower residual astigmatism 1

Critical Considerations for Surgical Planning

Axis Alignment:

• Cyclotorsion compensation is critical because failing to compensate results in axis misalignment and reduced astigmatic correction 1
• The use of a tracker or iris registration helps maximize accuracy of the astigmatic ablation axis 3

Optical Zone Size:

• Larger optical zones result in less undercorrection and fewer higher-order aberrations, particularly in high myopia, but require sufficient corneal thickness 1

Ocular Surface Optimization:

• The integrity of the ocular surface is critically important for accurately measuring corneal astigmatism 4
• Optimizing the ocular surface before surgery can significantly improve the accuracy of preoperative astigmatism measurements and refractive outcomes 4

Common Pitfalls to Avoid

• Never attempt full cylindrical correction immediately in adults with previously uncorrected astigmatism, as this leads to poor tolerance; gradual correction is better accepted 2, 1
• Irregular astigmatism (seen in keratoconus, corneal scarring, post-surgical corneas) cannot be fully corrected with spherocylindrical lenses and requires specialty contact lenses or surgical intervention 2, 1
• Obtain at least 2-3 measurements when measuring corneal astigmatism, and repeat measurements after optimizing the ocular surface if discrepancies occur 4
• Account for posterior corneal astigmatism and lens tilt in toric IOL planning, as these are important components of total corneal astigmatism 4

Contraindications to Refractive Surgery

Absolute contraindications include: 3

• Unstable refraction
• Abnormalities of the cornea (keratoconus, corneal ectasias, thinning, edema)
• Insufficient corneal thickness for proposed ablation depth
• Visually significant cataract
• Uncontrolled glaucoma
• Uncontrolled external disease (blepharitis, dry eye syndrome)
• Unrealistic patient expectations

Relative contraindications include: 3

• Significant irregular astigmatism
• Abnormal corneal topography/tomography indicating possible keratoconus
• History of herpes simplex virus or varicella zoster virus keratitis
• Inadequately controlled dry eye