Small incision lenticule extraction (SMILE) was first described by Sekundo et al.1 more than 5 years ago, and numerous studies have demonstrated its safety, efficacy, and stability in correcting myopia and myopic astigmatism.2–7 However, both intraoperative and postoperative complications have been reported.8,9 In cases of difficult lenticule dissection, there could be incomplete lenticule removal, leaving a lenticule remnant in the eye. This could result in irregular astigmatism and reduced visual acuity.10,11 We have encountered several cases of incomplete lenticule removal that were detected postoperatively, and we performed early secondary lenticule remnant removal in these cases.
We present 4 cases with a similar clinical course, summarized in Table 1. All cases had seemingly uneventful bilateral SMILE surgery but presented with reduced visual acuity and refractive surprise in one eye, whereas the fellow eye had uneventful recovery. Pentacam (Oculus Optikgeräte, Wetzlar, Germany) examination revealed an area of steepening and elevation (Figure 1A). On review of the surgical video, we could identify incomplete dissection of the lenticule, leaving behind a lenticular remnant at the inferior or inferotemporal part of the stromal pocket (Figures 1C–1D). All cases subsequently underwent secondary lenticule removal under local anesthesia. The small incision wound and the previous interface were reopened with careful dissection. Injection of balanced salt solution around the remnant caused it to swell up so its outline could be visualized. After further dissection around the remnant, it could be removed with forceps. Postoperatively, all four cases had immediate improvement of uncorrected distance visual acuity and refraction. Pentacam also showed improvement in the previously abnormal area (Figure 1B). The vision and refraction remained stable at 3 months postoperatively.
Characteristics of All Four Cases
Examples of the (A–B) Pentacam (Oculus Optikgeräte, Wetzlar, Germany) and (C–D) intraoperative images demonstrating the presence of lenticule remnant. (A) On postoperative day 1, the left eye of patient 2 revealed steepening and elevation in the inferotemporal area (red arrow). (B) At postoperative month 3, after the secondary remnant removal procedure, the left eye of patient 2 showed improvement in the previously steepened and thickened area (red arrow). (C) Review of the intraoperative surgical video of patient 1 (surgeon's view), showing the time frame after the lenticule was removed. The red arrows highlighted the edge of the residual lenticule remnant. (D) The left eye of patient 2 (surgeon's view) showing the time frame just after dissection but before inserting the forceps to remove the lenticule. Again, the red arrows highlighted the edge of the remnant and the yellow arrows showed the bunched-up lenticule, which would then be removed by forceps.
We have presented four cases of residual SMILE lenticule remnant removal. All cases had seemingly uneventful SMILE surgery, with no suction loss or other intraoperative complications. However, when we reviewed the intraoperative videos with increased magnification and screen size (compared with the intraoperative screen size), we could easily identify an area of incomplete dissection and the presence of lenticule remnant in all four cases (Figures 1C–1D). During the original surgery, we first dissected the anterior surface, followed by the posterior surface, and we aimed for a complete dissection. From our experience, the anterior dissection was invariably complete. It was during the posterior dissection that the probe punctured the lenticule button and entered a wrong plane, which resulted in incomplete dissection and created a remnant. We later learned that we had mistaken the edge of the remnant (Figures 1C–1D, red arrows) as the actual edge of the lenticule. Thus, during secondary surgery, we entered the residual lenticule posteriorly from the edge and injected balanced salt solution to highlight the outline of the lenticule remnant for better visualization to complete the dissection. Careful dissection was needed when reopening the incision and the stromal interface. The surgeon must avoid dissecting blindly, which would create stromal scarring. We found that the observer screen could sometimes provide a better view than the surgeon's microscope, which helped with identifying the surgical planes. The slit-lamp feature in the VisuMax laser platform (Carl Zeiss Meditec, Jena, Germany) was also useful for inspection and dissection of remnants.
An incomplete lenticule dissection was the cause of the residual lenticule remnant. Ivarsen et al.8 reported that 34 cases had lenticule extraction difficulties in a large series with 1,800 eyes. There was no difference in terms of preoperative characteristics or intraoperative laser settings in these cases compared with the other uncomplicated cases. Some cases of lenticule extraction difficulties resulted in postoperative irregular topographies. It was possible that residual lenticular remnants were present in these cases. In a case report by Dong and Zhou,10 there was also a suspected remnant after the corneal topography demonstrated an area of steepened corneal surface inferiorly, and corneal thickness was relatively thicker in this area than in others. They managed their case conservatively and noticed some improvement in uncorrected and corrected distance visual acuity, but at 5 months postoperatively the irregular astigmatism persisted and the corrected distance visual acuity was 20/25.
We suggest surgeons carefully analyze the topography maps and review the surgical videos in all cases with suboptimal visual and refractive outcomes. From our experience, anterior segment optical coherence tomography images were difficult to interpret in the early postoperative phase for the presence of a remnant. In our small series, we have demonstrated that secondary removal of the remnant instead of observation was feasible and could result in an immediate postoperative improvement in visual acuity, refraction, and topography. Nevertheless, as shown in our figure, irregularity on the topography after remnant removal was still present to some extent. This could be explained by the increased manipulation while reopening the stromal interface that affected the wound healing response, which we expect could normalize over time with longer follow-up.
We agree with Dong and Zhou10 that prevention is the best solution for this condition. It was important to completely dissect the lenticule and carefully examine the intactness of the lenticule during the surgery. In our first 50 cases of SMILE, we routinely examined the removed lenticule for completeness, but we did not continue this routine practice. We now believe we should readopt this step during every SMILE surgery. The presence of debris, mucus, or oil droplets on the ocular surface while the eye is coupled with the femtosecond laser docking cone can also block the femtosecond laser, increasing the subsequent difficulty in dissection.9 The surgeon should have a higher index of suspicion for incomplete dissection in eyes with a sticky flap or in lower correction cases with a thinner lenticule.
Our case series showed that preforming an early, secondary lenticular remnant removal operation was feasible, safe, and could result in improvement in both refraction and visual acuity.
- Sekundo W, Kunert KS, Blum M. Small incision corneal refractive surgery using the small incision lenticule extraction (SMILE) procedure for the correction of myopia and myopic astigmatism: results of a 6 month prospective study. Br J Ophthalmol. 2011;95:335–339. doi:10.1136/bjo.2009.174284 [CrossRef]
- Blum M, Taübig K, Gruhn C, Sekundo W, Kunert KS. Five-year results of small incision lenticule extraction (ReLEx SMILE). Br J Ophthalmol. 2016;100:1192–1195. doi:10.1136/bjophthalmol-2015-306822 [CrossRef]
- Ganesh S, Gupta R. Comparison of visual and refractive outcomes following femtosecond laser–assisted LASIK with SMILE in patients with myopia or myopic astigmatism. J Refract Surg. 2014;30:590–596. doi:10.3928/1081597X-20140814-02 [CrossRef]
- Kobashi H, Kamiya K, Ali MA, Igarashi A, Elewa ME, Shimizu K. Comparison of astigmatic correction after femtosecond lenticule extraction and small-incision lenticule extraction for myopic astigmatism. PLoS One. 2015;10:e0123408. doi:10.1371/journal.pone.0123408 [CrossRef]
- Lin F, Xu Y, Yang Y. Comparison of the visual results after SMILE and femtosecond laser-assisted LASIK for myopia. J Refract Surg. 2014;30:248–254. Erratum in: J Refract Surg. 2014;30:582. doi:10.3928/1081597X-20140320-03 [CrossRef]
- Reinstein DZ, Carp GI, Archer TJ, Gobbe M. Outcomes of small incision lenticule extraction (SMILE) in low myopia. J Refract Surg. 2014;30:812–818. Erratum in: J Refract Surg. 2015;31:60. doi:10.3928/1081597X-20141113-07 [CrossRef]
- Chan TC, Ng AL, Cheng GP, et al. Vector analysis of astigmatic correction after small-incision lenticule extraction and femtosecond-assisted LASIK for low to moderate myopic astigmatism. Br J Ophthalmol. 2016;100:553–559. doi:10.1136/bjophthalmol-2015-307238 [CrossRef]
- Ivarsen A, Asp S, Hjortdal J. Safety and complications of more than 1500 small-incision lenticule extraction procedures. Ophthalmology. 2014;121:822–828. doi:10.1016/j.ophtha.2013.11.006 [CrossRef]
- Ramirez-Miranda A, Ramirez-Luquin T, Navas A, Graue-Hernandez EO. Refractive lenticule extraction complications. Cornea. 2015;34(suppl 10):S65–S67. doi:10.1097/ICO.0000000000000569 [CrossRef]
- Dong Z, Zhou X. Irregular astigmatism after femtosecond laser refractive lenticule extraction. J Cataract Refract Surg. 2013;39:952–954. doi:10.1016/j.jcrs.2013.04.016 [CrossRef]
- Tong JY, Cherepanoff S, Males JJ. SMILE rescue: delayed lenticule removal in a patient with high myopia. J Refract Surg. 2017;33:199–202. doi:10.3928/1081597X-20170104-01 [CrossRef]
Characteristics of All Four Cases
|Parameter||Case 1||Case 2||Case 3||Case 4|
|Preop refraction (D) (with CDVA)||−3.00 −0.50 × 30 (1.0)||−4.00 −0.50 × 85 (1.0)||−2.25 (1.0)||−5.00 −0.37 × 175 (1.0)|
|Postop refraction (D) (with CDVA)||+2.50 −2.00 × 100 (0.9)||Failed (0.8)a||+1.50 −1.25 × 105 (1.0)||+0.75 −1.25 × 125 (1.0)|
|Postop UDVA (additional symptoms) (decimal)||0.4||0.5||0.7||0.6; monocular diplopia|
|Site of remnant||Inferior||Inferotemporal||Inferotemporal||Inferior|
|Remnant removal date||Day 2||Day 10||Day 9||Month 1|
|1 day after remnant removal refraction (D) (with CDVA)||pl −0.50 × 100 (1.0)||−0.75 −0.50 × 80 (1.0)||+0.75 −0.50 × 125 (1.0)||pl −1.00 × 135 (0.9)|
|UDVA 1 day after remnant removal (decimal)||0.8||0.8||0.9||0.6|
|3-month follow-up refraction (D) (with CDVA)||+0.50 −0.25 × 180 (1.0)||pl −0.25 × 105 (1.0)||+0.25 (1.0)||pl (1.0)|
|3-month follow-up UDVA (decimal)||1.0||0.9||1.0||1.0|