What is the preferred surgical correction for an adult with stable astigmatism, a clear cornea, central corneal thickness ≥500 µm, and no active ocular surface disease?

Surgical Correction for Astigmatism

For an adult with stable astigmatism, clear cornea, adequate central corneal thickness (≥500 µm), and no active ocular surface disease, LASIK or PRK are the preferred surgical options, with the choice depending primarily on patient lifestyle needs and recovery timeline preferences. 1

Primary Surgical Options

Excimer Laser-Based Keratorefractive Surgery

The 2023 American Academy of Ophthalmology Refractive Surgery Preferred Practice Pattern establishes excimer laser procedures as the standard approach for astigmatism correction in patients meeting your criteria 1. Two main techniques are available:

LASIK (Laser-Assisted In Situ Keratomileusis):

• Offers rapid visual recovery (typically within 24-48 hours)
• Minimal postoperative discomfort
• Requires adequate corneal thickness to maintain residual stromal bed ≥250 µm after creating flap and ablation 1
• With your patient's CCT ≥500 µm, LASIK is feasible for low to moderate astigmatism

PRK (Photorefractive Keratectomy):

• Surface ablation without flap creation
• Slower visual recovery (weeks rather than days) 1
• May be preferred when maximizing residual stromal bed thickness is critical
• Bilateral same-day PRK requires counseling that driving may not be possible for weeks 1

Critical Technical Considerations for Astigmatism Correction

Axis alignment is absolutely crucial for astigmatic correction—misalignment dramatically reduces treatment efficacy 1. The guidelines emphasize:

• Cyclotorsion compensation: Mark the operative eye while patient is seated upright before surgery, as ocular cyclotorsion occurs when transitioning from seated to supine position 1
• Iris registration or eye tracking: Use available technology to maximize axis accuracy 1
• Nomogram adjustment: For astigmatism correction, expect approximately 13% undercorrection in low-to-moderate astigmatism (<2.00 D) and 16% undercorrection in high astigmatism (>2.00 D). Increase nomogram values by 10% for target cylinder treatment, especially with preoperative astigmatism >0.75 D 2

Alternative Surgical Approaches

Small Incision Lenticule Extraction (SMILE/KLEx)

The 2025 evidence-based guidelines for keratorefractive lenticule extraction establish this as an emerging option 2. However, the nomogram adjustments for astigmatism are still being refined, with documented undercorrection rates requiring careful consideration.

Lenticular Refractive Surgery

When astigmatism on subjective refraction differs significantly from corneal topography findings, suspect lenticular astigmatism 1. In this scenario:

• Rule out early cataract formation
• Consider refractive lens exchange rather than keratorefractive surgery 1
• This is particularly relevant if significant lenticular component exists

Essential Preoperative Requirements

Before proceeding with any keratorefractive surgery 1:

Corneal topography/tomography is mandatory to:

• Exclude irregular astigmatism, keratoconus, or corneal ectasia
• Confirm regular astigmatism pattern
• Use Belin-Ambrosio enhanced ectasia display or similar indices to assess ectasia risk
• Abnormal topography is the most significant risk factor for postoperative ectasia 1

Contact lens discontinuation:

• Spherical soft lenses: 3 days to 2 weeks
• Toric soft lenses and rigid lenses: longer period due to greater corneal warpage potential
• Confirm refractive stability with multiple visits if needed 1

Ectasia risk assessment:

• Calculate percentage of tissue altered (PTA) = (Flap Thickness + Ablation Depth)/CCT
• PTA ≥40% associated with higher ectasia risk in context of normal topography 1
• Your patient's CCT ≥500 µm provides reasonable safety margin

Wavefront-Guided vs. Conventional Treatment

Some studies show wavefront-guided procedures result in fewer postoperative complaints of glare or halos under mesopic conditions compared to conventional treatments 1. However, the data on pupil size and postoperative visual quality remains controversial, with most studies failing to demonstrate a clear relationship 1.

Common Pitfalls to Avoid

1. Failing to compensate for cyclotorsion: This is the most common cause of axis misalignment in astigmatic treatments
2. Ignoring ocular residual astigmatism: Treating based solely on manifest refraction without considering the difference between refractive and corneal astigmatism results in residual postoperative astigmatism 3
3. Inadequate preoperative screening: Missing early keratoconus or forme fruste keratoconus on topography leads to catastrophic ectasia
4. Unrealistic patient expectations: Counsel about potential for night vision symptoms, dry eye, and need for enhancement procedures

Patient Counseling Requirements

The informed consent must address 1:

• Residual refractive error possibility
• Night-vision symptoms (glare, halos) may develop or worsen
• Dry eye symptoms may develop or worsen
• Small risk of loss of best-corrected visual acuity
• Impact on future IOL calculations for cataract surgery