Is SMILE Surgery Suitable for High Cylinder Power?

Table of Contents

• Understanding SMILE Surgery: A Brief Overview
• What is High Cylinder Power and How Does it Affect Vision?
• Can SMILE Surgery Correct High Cylinder Power?
• When SMILE May Not Be Enough for High Cylinder Power?
• Advantages and Disadvantages of SMILE Surgery for High Cylinder Power
• Combined Correction Techniques with SMILE Surgery
• Alternatives to SMILE for High Cylinder Cases
• Conclusion
• FAQs

Astigmatism, characterized by an abnormally curved or irregularly shaped cornea, is a common refractive error that leads to distorted and blurred vision at both near and distant ranges. Individuals having high astigmatism (cylinder power) often face challenges in day-to-day activities where crystal clear vision is required. Such visual disturbances can impact reading, night driving, computer work, and overall quality of life. Modern refractive surgery has revolutionized treatment options for patients with high astigmatism, and one prominent solution is SMILE (Small Incision Lenticule Extraction) surgery. As an advanced, flapless laser vision correction procedure, SMILE is increasingly chosen by patients and recommended by eye specialists, especially for those seeking reduced dependence on glasses or contact lenses. 

This blog by Planet Lasik provides a detailed examination of whether SMILE surgery is suitable for individuals with high cylinder power, highlighting clinical advancements and practical considerations.

Understanding SMILE Surgery: A Brief Overview

SMILE surgery stands for Small Incision Lenticule Extraction and has emerged as a cutting-edge advancement in the field of refractive surgery. Unlike traditional LASIK surgery, which requires creating a large corneal flap to access deeper corneal tissues, SMILE utilizes a femtosecond laser to carve a small disc-shaped piece of tissue (lenticule) within the cornea. This lenticule is then extracted through an incision as small as 2 to 4 millimeters, substantially smaller than the flaps used in LASIK. SMILE’s minimally invasive nature translates to several benefits: 

• Reduced postoperative discomfort 
• Less risk of dry eyes
• Quicker healing 

What is High Cylinder Power and How Does it Affect Vision?

‘Cylinder power’ refers specifically to the correction needed for astigmatism, a refractive error caused by uneven curves on the corneal surface. High cylinder power is usually defined as astigmatism greater than 2.00 diopters, though in clinical practice, cases over 3.00 diopters are often categorized as “high.” The optical consequence of high cylinder power is light focusing at multiple points on the retina, rather than a single clear point. The result is a spectrum of visual symptoms that may include:

• Blurred or shadowed vision at all distances
• Eye strain and headaches, especially while reading or using computers
• Difficulty in distinguishing fine details or reading small print
• Poor night vision, halos, or glare around lights
• Inconsistent vision quality throughout the day
• Difficulty with depth perception

Left uncorrected, high astigmatism can drastically affect everyday tasks and is also a significant risk factor for amblyopia (lazy eye) in paediatric patients if not promptly treated. 

Can SMILE Surgery Correct High Cylinder Power?

SMILE is clinically approved for treating myopia (short-sightedness) and moderate and some cases of high cylinder power. With recent upgrades in laser technology and preoperative mapping, SMILE astigmatism correction technique can now treat astigmatism up to 5.00 diopters. The factors that influence the suitability and effectiveness of SMILE for high cylinder cases include:

• Corneal Thickness: Adequate residual corneal tissue after lenticule extraction is mandatory to maintain corneal stability and minimize ectasia risk.

• Corneal Regularity: The shape and structural integrity of the cornea play a crucial role; highly irregular or scarred corneas may not be ideal candidates.

• Pupil Centration and Eye Tracking: Advanced systems ensure that laser pulses are precisely delivered, even if minor eye movements occur, which is vital for correcting significant cylinder errors.
• Coexisting Eye Problems: Conditions such as dry eye syndrome, keratoconus, or a history of previous ocular surgeries may impact candidacy and postoperative outcomes.

A thorough preoperative assessment involves corneal topography, pachymetry (thickness mapping), ocular surface analysis, and individualized risk stratification. 

When SMILE May Not Be Enough for High Cylinder Power?

Although SMILE is a powerful solution for many patients with astigmatism, its capabilities have limits. It may not be the optimal approach for those with very high cylinder power (commonly above 5.00 diopters) or thin corneas. For such patients, relying solely on SMILE might result in under-correction or visual outcomes that do not match expectations. Some situations where SMILE alone may not suffice include:

• Severe Corneal Irregularity: If the corneal surface is not uniform, achieving perfect alignment for astigmatism correction is challenging.

• Cases with Mixed Astigmatism: Patients who exhibit both myopic and hyperopic astigmatism may require a different surgical approach.
• Teenagers or Progressive Astigmatism: Children and young adults whose refractive error is still changing may not be suited for surgical correction yet.

The presence of conditions like dry eyes, keratoconus, or prior corneal surgeries may further restrict ideal surgical options. “In such cases, surgeons may recommend advanced cylinder correction techniques for better outcomes.

Advantages and Disadvantages of SMILE Surgery for High Cylinder Power

Advantages:

Minimally Invasive: Eliminates the need for a corneal flap, preserving corneal biomechanics and natural strength.

Quick Recovery: Most patients report clear vision within 24–48 hours and resume their normal routine quickly.

Comfort and Convenience: Short procedure (10-15 minutes per eye), little or no pain, and limited restrictions on activities during healing.

Ideal for Active Lifestyles: Minimizes risk of post-surgery displacement or trauma complications.

Disadvantages:

Correction Range: While expanding, SMILE’s treatable cylinder range is still narrower than some other procedures, particularly for extreme or highly irregular astigmatism.

Learning Curve: SMILE requires substantial surgical expertise; choosing a well-experienced center or surgeon is crucial.

Combined Correction Techniques with SMILE Surgery

For select patients with high or complex cylinder power, a combination approach may lead to superior results. Some SMILE combined with other surgery possibilities include:

SMILE + PRK: Surface ablation with PRK surgery may be performed after initial SMILE to correct a small leftover cylinder or refine visual results. This staged approach allows the preservation of corneal tissue while extending the treatable ranges.

SMILE + Contoura Vision: In rare, selected cases, a modification using topography-guided LASIK (e.g., Contoura Vision) may help fine-tune astigmatism correction in eyes with unique corneal shapes.

Early Enhancement: Careful monitoring post-SMILE enables early detection and timely enhancement of residual astigmatism.

Combining procedures necessitates detailed diagnostic images, advanced planning (often with AI and corneal modeling), and highly experienced refractive surgeons. 

Alternatives to SMILE for High Cylinder Cases

Not all patients are candidates for SMILE. Alternative refractive surgery options include:

Conclusion

SMILE surgery represents a remarkable advancement in refractive laser eye surgery, especially appropriate for many patients with moderate to high cylinder power. Its minimally invasive design, rapid recovery, comfort, and ability to address common astigmatism types have made it a patient-favorite for those seeking freedom from glasses or lenses. However, it is not universally suitable; patients with very high or irregular astigmatism may benefit more from alternative (or combined) correction techniques such as PRK, Contoura Vision, or even lens-based interventions.

For detailed advice or to schedule a clinical evaluation, consult the experienced refractive surgery team at Planet Lasik by Centre for Sight, where advanced technology and compassionate care are at the heart of your vision journey.

FAQs

• Can SMILE correct 3.00 diopters of cylinder power?
  SMILE surgery can correct up to 5.00 diopters of cylinder power, depending on individual patient factors.

• Is enhancement possible after SMILE surgery?
  Enhancements are possible after SMILE surgery if residual astigmatism remains.

• Which is better for high astigmatism – SMILE or Contoura Vision?
  For high astigmatism, Contoura Vision may provide more precise correction due to its topography-guided approach.

• Can SMILE be combined with PRK or LASIK?
  Additionally, SMILE can be combined with PRK or LASIK for a more comprehensive treatment plan.