MAY 12, 2014
This large retrospective study found that small-incision lenticule extraction (SMILE) had an acceptable overall safety profile in myopic patients. However, a relatively high percentage of patients lost visual acuity in the first three postoperative months and didn’t fully recover it until one year.
SMILE is currently undergoing clinical trials in the United States. Although it avoids the use of two lasers and complications related to a LASIK flap, ultimately it will have to demonstrate significant overall benefit and lower complications than LASIK.
The authors reviewed SMILE outcomes in 922 healthy patients (1,800 eyes) treated for myopia or myopic astigmatism at a single center in Denmark. Intraoperative complications occurred in a small percentage of eyes and were visually significant only in one eye.
At three months postop, CDVA was unchanged or improved in 86 percent of eyes. However, 1.5 percent of eyes lost two or more lines. At a late follow-up visit (average, 18 months), CDVA was within one line of the preoperative level in all eyes. Irregular corneal topography occurred in an additional 18 eyes (1 percent), resulting in reduced three-month CDVA or ghost images.
Although overall complications were low, it is concerning that irregularity occurred in a relatively high percentage of patients in this study. While the authors are unsure of the basis for these irregularities, they did note difficulties in lenticule extraction in five of these eyes, suggesting the implication of perioperative complications. In one recent case report, a lenticule remnant was found to be the reason for postoperative irregular topography.
Another potential explanation could be irregular cleavage of tissue bridges after the laser cut. An opaque bubble layer during surgery would increase the amount of tissue bridges; however, opaque bubble layers were not observed in this series. They also note that a significant number of patients with irregular topography were treated at laser setting 1, indicating that optimization of laser settings may further reduce the frequency of these complications.