SMILE Trends and Growth
The FDA approved SMILE in the United States in 2016.1 Since then, SMILE has been gaining popularity, with over 12 million eyes treated worldwide. Notably, 80% of procedures in the Asia-Pacific region are SMILE, and the number of SMILE surgeries significantly exceeds that of LASIK.2
“In my opinion, the future of refractive surgery is shifting towards a lenticular extraction versus flap creation for a variety of reasons,” says Dr. Moarefi. Global growth has seen 200% increase in laser vision correction over the last 10 years, and his practice has been performing more SMILE procedures than LASIK and currently uses SMILE for around 60% of cases (Figure 1).
Figure 1. SMILE Accounts for 60% of Dr. Moarefi’s Laser Vision Correction Practice
Advantages for Patients
SMILE is a minimally invasive procedure that requires only a small incision of about 2 to 4 mm, in contrast to the larger flap creation needed for LASIK. This smaller incision preserves more corneal strength and reduces the risk of complications, leading to faster recovery and greater patient comfort. Patients who undergo the SMILE procedure often experience less dryness and quicker healing of the corneal nerves.1 Additionally, since there is no flap involved, complications associated with flaps—such as microstriae, macrostriae, or rolled edges—are low.
Dr. Tseng comments that “for any patients that might be a little bit more risk averse as far as having a flap, whether they be, athletes or people who live an active lifestyle or just in general worried about potentially rubbing their eyes, causing the flap to dislodge or shift, SMILE results in a much easier process and reassures them that without a flap, they can still enjoy vision correction.”
Patients can resume their normal activities much sooner thanks to a rapid recovery process. This procedure alleviates dry eye symptoms, which is especially advantageous for individuals who are prone to dryness, such as older adults or those with meibomian gland dysfunction. For those with active lifestyles, SMILE provides a significantly faster return to activities such as workouts, swimming, and surfing compared to LASIK.
Dr. Moarefi noted that some patients may have concerns about SMILE because they are more familiar with LASIK. The literature shows that SMILE has visual outcomes similar to those of LASIK.1 A meta-analysis comparing SMILE and femtosecond LASIK for dry eye outcomes shows that SMILE demonstrates superior performance across multiple parameters, including TBUT, conceal sensitivity, OSDI, and Schirmer test results.3 Additionally, a military study comparing lenticular extraction, PRK, and LASIK found no difference in vision outcomes and, in some cases, that lenticular extraction outperformed PRK.4
Surgical Details
The SMILE procedure utilizes a femtosecond laser to create four key incisions: a posterior lenticular cut, an anterior cap cut, and two small side incisions. These small incisions facilitate the easy removal of the refractive lenticule through the 2- to 4-mm cap-opening incision. Creating these cuts typically takes about 7 seconds with the SMILE Pro device.
Dry and wet refractions are crucial for determining the target. The lenticular parameters for SMILE are primarily predetermined. The minimum thickness of the lenticule is set at 15 microns, while the cap thickness, which is similar to flap thickness, is fixed at 120 microns. Additionally, the cap is approximately 1 mm larger than the lenticule, which allows the surgeon to dissect the lenticule out.
Candidacy and Contraindications
In the U.S., SMILE and SMILE Pro are indicated for myopia (-1.00 to -10.00 D), with or without astigmatism (-0.75 to -3.00 D).1 “To be more specific, we want to always just make sure that the spherical equivalent in any direction, any axis, does not exceed -10.00,” says Dr. Tseng,
Contraindications generally mirror those of LASIK candidacy:
- The residual stromal bed thickness should not go below 250 microns.
- Patients should have a clean topography and keratometry to rule out keratoconus or irregular corneal findings.
- Patients with active autoimmune or connective tissue disease, uncontrolled diabetes, uncontrolled glaucoma, or conditions that might cause severe dry eye, or current use of drugs like Accutane, are generally contraindicated (Figure 2).
Figure 2. SMILE Contraindications
Post-Operative Care
The post-operative care for SMILE is quite similar to that for LASIK, with many common elements (Figure 3). Typically, patients are prescribed prophylactic antibiotics and anti-inflammatory medications, which are taken four times a day for approximately one week. For those with higher prescriptions, a second week of anti-inflammatory treatment may be recommended to enhance comfort and reduce light sensitivity. Patients are still advised to use artificial tears, typically four times a day initially, but they often reduce use to "as needed" by week one or two.
Figure 3. SMILE Post Operative Care
Post-operative care is simpler due to fewer complications. Since there is no flap, a post-operative day one visit is not strictly necessary, although many patients still come in; a one-week visit is also acceptable.
There are no flap-related complications (such as microstriae or flap-edge issues) or concerns about Diffuse Lamellar Keratitis (DLK), which simplifies co-management for optometrists (ODs). “No flap, no flap complications, no issues where you feel like, well, I don't know if the edge is a little retracted… Do I need to send them back to the MD, or is the microstriae significant enough to cause vision problems? Do I need to send them back to the original doctor? … these kinds of issues you don't end up seeing because, again, there's no flap involvement,” says Dr. Tabanfar.
Patients can typically return to work, shower, and perform most normal activities (including driving and going to the gym) on day one. Light makeup is acceptable, but heavy eye makeup is discouraged for a week. Patients are advised to avoid contact sports and any activity that involves rubbing the eyes for a week.
Dry eye management is easier with SMILE, and patients experience less severe vision fluctuations in the initial weeks. Patients with smile tend to experience fewer higher-order aberrations, which supports better optical quality.5
In conclusion, SMILE has gained popularity among patients, especially those with active lifestyles, due to its focus on preserving corneal strength and reducing flap-related complications. The post-operative care for SMILE is similar to that for LASIK and typically involves antibiotics and anti-inflammatory medications; however, it is typically simpler because SMILE has fewer complications. Additionally, SMILE can help grow your practice while benefiting patients.
