How it Works
SMILE is a femtosecond laser procedure designed to correct nearsightedness. The laser first creates a disc (lenticule) of tissue within the cornea without lifting a flap or removing the epithelium. A 2.5mm to 3mm incision is made, through which the surgeon removes the lenticule. The result is the same as myopic LASIK because the amount of tissue removed is the same.1
As with other refractive procedures, the ocular surface needs to be healthy, and dry eye should be treated prior to the procedure. Ideal patients should have no signs of ocular disease in the anterior or posterior segment. Corneal topography should be normal with no evidence of irregular astigmatism or keratoconus. Currently, SMILE is approved to correct myopia of -1.00D to -8.00D with -0.50D or less of cylinder in patients 22 years or older with stable nearsightedness that has changed by no more than 0.50D in the year. SMILE can treat astigmatism in Europe now, and hopefully in the United States in the future.
Some advantages of SMILE over LASIK include fewer symptoms of dry eye, less compromised corneal sensation and, possibly, greater biomechanical stability.2-4
Unfortunately, patients who need an enhancement must have a secondary PRK to ensure it does not interfere with the original SMILE procedure. In addition, SMILE is only FDA approved to treat spherical myopia, limiting the patient population indicated for the procedure.
Similar to LASIK, follow-up care usually consists of one day, one week, one month, three month, six month and one year visits. A typical postoperative drop regimen consists of a broad-spectrum antibiotic QID for one week and a steroid QID for one week then BID for one week.
With SMILE, patients often enjoy fewer dry eye symptoms and a faster visual recovery more comparable with LASIK than PRK.2-4
SMILE is still a tissue subtraction surgery and comes with a few concerns. Clinicians must monitor corneal topographies and warn patients against post-op eye rubbing because it can lead to corneal ectasia. As with LASIK, diffuse lamellar keratitis is possible during the post-op period. This can be managed with a short course of steroid drops, and patients rarely need a referral back to the surgeon to rinse the interface. Conditions such as dry eye and epithelial ingrowth can occur after SMILE and are treated the same as in LASIK patients.
Because SMILE comanagement is similar to that of LASIK and PRK—which we have been doing since the 1990s—we can be just as confident when caring for SMILE patients.
Drs. Rasmussen and Schweitzer practice at Vance Thompson Vision in Sioux Falls, SD, and are adjunct professors at the Illinois College of Optometry.
1. Liu M, Chen Y, Wang D, et al. Clinical outcomes after SMILE and femtosecond laser-assisted LASIK for myopia and myopic astigmatism: a prospective randomized comparative study. Cornea. 2016;35(3):210-6.