SMILE and FemtoLASIK: What to Compare Before Deciding
Dr. Guillermo Enríquez TostadoNovember 8, 202610 min read
In this article
Summary: SMILE and FemtoLASIK are refractive surgery procedures intended to reduce dependence on glasses or contact lenses by changing the shape of the cornea. Although they may offer comparable visual results for selected people, they are not interchangeable for all refractive errors and do not have the same surgical design, recovery profile, or options for customization. The decision should be based on each person’s prescription, refractive stability, corneal and ocular surface health, expectations, and activities.
What Are SMILE and FemtoLASIK?
In general, both procedures use lasers to change the shape of the cornea and alter its focusing power. This can help correct refractive errors such as myopia and astigmatism; FemtoLASIK may also be used to treat hyperopia, depending on the equipment, the authorized indication, and the relevant clinical assessment. The FDA explains that the main refractive errors are myopia, hyperopia, and astigmatism.
In SMILE, a femtosecond laser creates a small lens-shaped piece of tissue inside the cornea, called a lenticule. The surgeon removes it through a small incision without creating a corneal flap. The procedure is described in the FDA VisuMax Laser Patient Information Booklet.
In FemtoLASIK, a femtosecond laser creates a thin flap in the cornea. Then, an excimer laser reshapes the exposed corneal tissue, and the flap is repositioned. An explanation of the procedure is available in the National Eye Institute information on surgery for refractive errors.
What refractive errors can each procedure address?
The exact indication depends on the technology platform and applicable regulations. Therefore, prescription ranges should not be interpreted as a guarantee of individual candidacy.
For SMILE, the U.S. indication for the VisuMax laser reviewed covers myopia from -1.00 to -10.00 diopters, astigmatism from -0.75 to -3.00 diopters, and a spherical equivalent of up to -10.00 diopters, in people aged 22 or older whose prescription has been stable for the preceding year. These ranges apply to that device and not necessarily to all equipment available in other countries or clinics; they can be reviewed in the FDA Summary of Safety and Effectiveness and its authorization record.
FemtoLASIK may be used to treat myopia, hyperopia, and astigmatism, but the permitted ranges vary depending on the laser, treatment profile, and applicable authorization. The FDA notes that each approved laser has specific treatment ranges. Therefore, it is not enough to say that someone “has the right prescription”: the prescription’s stability, corneal shape and thickness, ocular surface health, and other safety factors also need to be confirmed.
Neither technique corrects presbyopia, the progressive difficulty focusing up close that develops with age. The National Eye Institute warns that many people will need reading glasses at some point, even after successful refractive surgery.
Technical Differences Worth Comparing
- •Corneal tissue — SMILE: Removes a lenticule through a small incision. · FemtoLASIK: Creates a flap and reshapes the cornea with an excimer laser.
- •Flap — SMILE: Does not create a corneal flap. · FemtoLASIK: Does create a flap, which remains an anatomically relevant structure.
- •Customization — SMILE: Treatment options may be more limited depending on the equipment and prescription. · FemtoLASIK: Wavefront- or topography-guided profiles may be available when indicated and offered.
- •Myopia and astigmatism — SMILE: May be an option for certain ranges of myopia, with or without astigmatism. · FemtoLASIK: Can also treat myopia and astigmatism within authorized ranges.
- •Hyperopia — SMILE: Should not be assumed to be an available indication; the equipment’s authorization needs to be confirmed. · FemtoLASIK: May be considered depending on the platform and clinical assessment.
- •Possibility of enhancement later — SMILE: A different approach may be needed if residual refractive error remains. · FemtoLASIK: Access to the flap may make some retreatments easier, although not everyone is a candidate.
Scientific comparisons do not show a universal winner. A meta-analysis of randomized clinical trials found generally comparable results for SMILE and LASIK in treating myopia and astigmatism, although it reported a slight advantage for LASIK in refractive predictability and less spherical aberration after SMILE. The quality and combination of the studies should be considered when interpreting these results; see the article by Yao and colleagues on SMILE and LASIK.
Ocular surface, sensitivity, and visual quality
One possible consideration in favor of SMILE is that it avoids creating a flap and may affect fewer corneal nerve fibers during the first few months. A meta-analysis of studies comparing SMILE with FemtoLASIK found more dry eye symptoms and lower corneal sensitivity with FemtoLASIK at six months, although the overall quality of the evidence was low or very low. These findings do not mean that SMILE eliminates the risk of dryness or that everyone will have the same experience. The review is available on PubMed.
For astigmatism, a meta-analysis of 2023 found generally equivalent visual and refractive outcomes, but noted a tendency toward some undercorrection with SMILE, especially in certain ranges of low to moderate astigmatism. The analysis was published in the American Journal of Ophthalmology.
FemtoLASIK may be preferable when customized topography-guided or wavefront-guided treatment is needed, if that approach is indicated and available. It is also often considered when a rapid initial visual recovery is desired. However, the speed of recovery is not a guarantee of a perfect result and does not eliminate the risks of surgery.
Before any procedure, it is important to identify and treat problems such as dry eye, blepharitis, or abnormalities of the tear film. A comprehensive preoperative evaluation usually includes measurement of the eyeglass prescription, corneal topography or tomography, corneal thickness, an examination of the ocular surface, and a general eye exam. The American Academy of Ophthalmology, through EyeWiki, describes these assessment elements.
What may influence the decision?
The choice should be individualized. SMILE may be reasonable for some people with nearsightedness, especially when there is concern about dry eye, they play contact sports, or their occupation puts them at risk of eye injuries, because no flap is created. This does not mean it is automatically safer for every patient or that it eliminates the risk of corneal complications.
FemtoLASIK may be considered when farsightedness needs to be corrected, a customized profile is needed, or a future enhancement may need to be facilitated, provided the eye’s anatomy and the equipment allow it. For low or moderate astigmatism, some studies have found greater predictability with LASIK, although the individual difference may be small and does not determine the choice on its own.
Alternatives should also be discussed. If the cornea, ocular surface, or eyeglass prescription is not suitable for a corneal procedure, contact lenses, continuing to wear glasses, PRK, or other options may be considered, depending on the case. The consultation should include realistic goals: reducing dependence on glasses or contact lenses is not the same as guaranteeing complete, permanent independence.
Risks and realistic expectations
Both SMILE and FemtoLASIK may be associated with dryness, blurred vision, halos, glare, light sensitivity, visual fluctuations, residual refractive error, the need for glasses for certain activities, and, in rare cases, corneal complications or vision loss. For LASIK, the National Eye Institute also mentions infection, healing problems, and the possibility of needing another surgery.
The surgery is permanent and cannot be reversed as if contact lenses were simply removed. In addition, the result may change over time because of changes in refractive error, aging of the eye, or the onset of presbyopia. Before deciding, it is a good idea to ask which technique and equipment are being proposed, what range of refractive error is authorized for that device, what alternatives are available, and how residual refractive error would be managed.
Frequently asked questions
Is SMILE better than FemtoLASIK?
Not universally. SMILE may offer advantages related to the absence of a flap and initial preservation of corneal sensitivity in some studies. FemtoLASIK may offer greater customization and rapid initial visual recovery. The best option depends on the individual evaluation.
Can I choose SMILE if I have farsightedness?
It should not be assumed. Whether SMILE is indicated depends on the equipment and applicable authorization; the FDA documentation consulted for VisuMax applies to nearsightedness with or without astigmatism. For farsightedness, it is necessary to confirm whether there is a valid indication for the available platform.
Will I stop wearing glasses forever after either procedure?
There is no guarantee of permanent freedom from glasses. Some people may need them for reading, driving at night, specific tasks, or if a residual refractive error remains. Presbyopia develops with age and is not corrected by SMILE or conventional FemtoLASIK.
Conclusion
Comparing SMILE vs. FemtoLASIK means looking beyond the name of the procedure. Your prescription, type of refractive error, cornea, ocular surface, activities, potential to personalize treatment, and expectations should all be part of the decision. A comprehensive ophthalmologic assessment can determine whether either of these options is reasonable or whether an alternative should be considered.
If you’d like to explore your options for reducing your dependence on glasses, you can request an assessment through the office’s WhatsApp. The availability of SMILE, FemtoLASIK, equipment, and treatment profiles should be confirmed directly before attributing them to the office.
References
- •National Eye Institute. Surgery for Refractive Errors. Updated on 6 December 2024.
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- •Song J, et al. SMILE Versus LASIK for Astigmatism Corrections: A Systematic Review and Meta-analysis. American Journal of Ophthalmology, 2023.
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This content is for informational purposes and does not replace a medical consultation or constitute a diagnosis.
This information is for guidance only and does not replace a medical consultation, diagnosis, or treatment. Each case is assessed in person.
