Journal of Refractive Surgery

Original Article Supplemental Data

Postoperative Corneal Complications in Small Incision Lenticule Extraction: Long-Term Study

Yan Wang, MD, PhD; Jiaonan Ma, MD; Lin Zhang, MD, PhD; Haohan Zou, MD; Jinxiao Li, MD; Yue Zhang, MD; Vishal Jhanji, MD

Abstract

PURPOSE:

To investigate the incidence and clinical results of corneal complications after small incision lenticule extraction (SMILE).

METHODS:

A retrospective cohort study including 3,223 patients (6,373 eyes) who were treated for myopia or myopic astigmatism was conducted. Postoperative corneal complications were recorded. Postoperative follow-up visits were scheduled on days 1 and 7 and months 1, 3, 6, and 12.

RESULTS:

Of the 6,373 cases, 432 eyes (6.8%) developed at least one corneal complication postoperatively. These included punctate epithelial erosions (3.26%), diffuse lamellar keratitis (DLK) (2.17%), corneal infiltrates (0.39%), interface debris/secretion (0.30%), interface haze (0.17%), interface foreign body (0.24%), corneal striae (0.14%), corneal edema (0.09%), and epithelial ingrowth (0.02%). Of cases with corneal complications, 308 (71.3%) had an uncorrected distance visual acuity (UDVA) of better than 20/25 and 49 (11.3%) eyes lost two or more lines of corrected distance visual acuity (CDVA) on the first day after surgery. By 3 months, only 2 eyes (0.9%) had lost two or more lines of CDVA. At 6 months, 1 eye (1.0%) did not achieve a UDVA of 20/25 as a result of stage 3 DLK, but achieved 20/20 by 1 year. The postoperative spherical equivalent in cases without complications was lower than that in cases with complications at 1 day and 1 and 3 months (P = .001, .011, and .001, respectively), but there was no statistical difference at 6 and 12 months.

CONCLUSIONS:

In this large cohort study, a variety of corneal complications were noted after SMILE. Although some of these complications may temporarily affect visual recovery, most resolve with appropriate treatment.

[J Refract Surg. 2019;35(3):146–152.]

Abstract

PURPOSE:

To investigate the incidence and clinical results of corneal complications after small incision lenticule extraction (SMILE).

METHODS:

A retrospective cohort study including 3,223 patients (6,373 eyes) who were treated for myopia or myopic astigmatism was conducted. Postoperative corneal complications were recorded. Postoperative follow-up visits were scheduled on days 1 and 7 and months 1, 3, 6, and 12.

RESULTS:

Of the 6,373 cases, 432 eyes (6.8%) developed at least one corneal complication postoperatively. These included punctate epithelial erosions (3.26%), diffuse lamellar keratitis (DLK) (2.17%), corneal infiltrates (0.39%), interface debris/secretion (0.30%), interface haze (0.17%), interface foreign body (0.24%), corneal striae (0.14%), corneal edema (0.09%), and epithelial ingrowth (0.02%). Of cases with corneal complications, 308 (71.3%) had an uncorrected distance visual acuity (UDVA) of better than 20/25 and 49 (11.3%) eyes lost two or more lines of corrected distance visual acuity (CDVA) on the first day after surgery. By 3 months, only 2 eyes (0.9%) had lost two or more lines of CDVA. At 6 months, 1 eye (1.0%) did not achieve a UDVA of 20/25 as a result of stage 3 DLK, but achieved 20/20 by 1 year. The postoperative spherical equivalent in cases without complications was lower than that in cases with complications at 1 day and 1 and 3 months (P = .001, .011, and .001, respectively), but there was no statistical difference at 6 and 12 months.

CONCLUSIONS:

In this large cohort study, a variety of corneal complications were noted after SMILE. Although some of these complications may temporarily affect visual recovery, most resolve with appropriate treatment.

[J Refract Surg. 2019;35(3):146–152.]

Small incision lenticule extraction (SMILE) has emerged as a novel technique for the correction of myopia.1,2 The clinical results are comparable to those of femtosecond laser–assisted laser in situ keratomileusis (FS-LASIK).3–7 In SMILE, a femtosecond laser is used to create an intrastromal lenticule that is manually extracted through a small incision.1,2 Because the SMILE procedure is flapless, not requiring the creation of a corneal flap, this surgical approach is not associated with the typical flap-related complications, such as incomplete flap dissection, free flap, flap buttonhole, and flap dislocation, typically seen in FS-LASIK.8,9 However, being a relatively new procedure, it has its own challenges and myriad postoperative complications. Recognition and management of these complications are essential to achieve good postoperative results. In the current study, we evaluated the corneal complications of SMILE in a large cohort of patients who underwent SMILE.

Patients and Methods

Study Population

This retrospective study evaluated eyes of consecutive patients who underwent SMILE for correction of myopia and myopic astigmatism between January 2013 and November 2017 at the Refractive Surgery Centre of Tianjin Eye Hospital, Tianjin Medical University, Tianjin, China. The study was conducted in accordance with the tenets of the Declaration of Helsinki and was approved by the ethics committee of Tianjin Eye Hospital. Written informed consent was obtained from all patients before the procedure.

Inclusion Criteria

The inclusion criteria for surgery were: age between 18 and 45 years, stable refraction for at least 2 years before the surgery, myopic spherical refraction from −0.50 to −10.00 diopters (D), myopic cylindrical refraction up to −5.00 D, corrected distance visual acuity (CDVA) of better than 20/25, and estimated residual thickness of the stromal bed greater than 250 µm. Eyes with a history of ocular surgery, severe dry eye, progressive corneal degeneration, keratoconus, and suspected keratoconus were excluded. Patients were asked to stop using soft and rigid contact lenses for 2 and 4 weeks prior to the surgery, respectively.

All patients were evaluated preoperatively and at days 1 and 7 and months 1, 3, 6, and 12 postoperatively. The examinations included assessment of uncorrected distance visual acuity (UDVA) and CDVA, manifest and cycloplegic refraction, slit-lamp biomicroscopy, and Scheimpflug topography (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany).

Surgical Procedure

SMILE was performed using the VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany) with a 500-kHz repetition rate. A small curved interface cone was used in all cases. The laser cutting was performed in the following automated sequence: posterior surface of the lenticule (spiral in pattern), lenticule side cut, and anterior surface of the lenticule (spiral out pattern), followed by a side cut on the cap. The laser energy was 110 to 175 nJ. The intended thickness of the cap was 110 or 120 µm. The diameters of the cap and lenticule were 7 to 8 and 6 to 7 mm, respectively. A 2-to 4-mm side cut for lenticule extraction was created at the 12-o'clock position. A spatula was inserted through the cut over the roof of the refractive lenticule dissecting this plane followed by the bottom of the lenticule. The lenticule was subsequently grasped and removed through the small incision. After removal of the lenticule, the incision was flushed with balanced salt solution. Postoperatively, ofloxacin 0.3% (Tarivid; Santen, Inc., Osaka, Japan) eye drops were administered four times daily for 3 days and fluorometholone 0.1% (Flumetholon; Santen, Inc.) eye drops were administered four times daily for 2 weeks and then tapered off over the following 2 weeks.

Statistical Analysis

The complications during SMILE were systematically registered in patient records and evaluated by a thorough review of these records of all patients. Statistical analysis of visual acuity was based on logMAR units. Continuous variables are expressed as the mean ± standard deviation, whereas categorical variables are expressed as frequencies and percentages. A P value of less than .05 was considered statistically significant. Data analysis was performed using SPSS software (version 22.0; SPSS, Inc. Chicago, IL).

Results

The study enrolled 6,373 eyes from 3,223 patients who underwent SMILE surgery. Table 1 shows the baseline characteristics of these cases. A total of 432 eyes (6.78%) developed at least one corneal complication after SMILE, as demonstrated in Table 2.

Preoperative Demographics

Table 1:

Preoperative Demographics

Corneal Complications After SMILE

Table 2:

Corneal Complications After SMILE

Punctate Epithelial Erosions

Punctate epithelial erosions occurred in 208 eyes with an incidence of 3.3%, of which 31 eyes (14.9%) were diagnosed on the first day, 75 eyes (36.1%) at 1 week, 74 eyes (35.6%) at 1 month, 26 eyes (12.5%) at 2 months, and 2 eyes (1.0%) at 3 months postoperatively. Punctate epithelial erosions affected the inferior cornea in 136 eyes (65.4%), central cornea in 51 eyes (24.5%) (Figure A, available in the online version of this article), superior cornea in 8 eyes (3.9%), nasal cornea in 8 eyes (3.9%), and temporal cornea in 5 eyes (2.4%). The punctate epithelial erosions resolved with the use of artificial eye drops in all but 2 eyes (1%), which required treatment with deproteinized calf blood extract two times daily for 1 week. After treatment, epithelial erosions resolved in 21 eyes (10.1%) after 1 week, 81 eyes (38.9%) after 1 month, 73 eyes (35.1%) after 2 months, 31 eyes (14.9%) after 3 months, and 2 eyes (1%) after 6 months.

Slit-lamp photograph showing different postoperative corneal complications: (A) corneal epithelial erosion, (B) haze (grade 0.5), (C) interface debris, (D) infiltration with inflammatory cells, (E) interface blood, and (F) striae.

Figure A.

Slit-lamp photograph showing different postoperative corneal complications: (A) corneal epithelial erosion, (B) haze (grade 0.5), (C) interface debris, (D) infiltration with inflammatory cells, (E) interface blood, and (F) striae.

DLK

DLK developed in 138 eyes (2.2%). Based on the classification by Linebarger et al.,10 we observed stage 1 DLK in 126 eyes (91.3%), stage 2 DLK in 9 eyes (6.5%), and stage 3 DLK in 3 eyes (2.2%). None of the patients developed stage 4 DLK. All cases of DLK manifested on day 1 postoperatively. Figure B (available in the online version of this article) presents the different morphology of different stages of DLK during the slit-lamp examination.

Slit-lamp photograph of eyes with different grades of diffuse lamellar keratitis (DLK) on the first postoperative day. (A) An eye with grade 1 DLK. A faint infiltrate in the cap periphery, especially in the peripheral interface around the small incision (red circle). (B) An eye with stage 2 DLK. Diffuse cellular infiltration in the interface but did not extend beyond the edge of the cap (red circle). (C) An eye with stage 3 DLK. A powdery cellular infiltration of the interface, involving the visual axis with multiple, fine granular collections clumped centrally. (D) With a narrow beam, the slit-lamp image showed a highly reflective structure in interface (arrow).

Figure B.

Slit-lamp photograph of eyes with different grades of diffuse lamellar keratitis (DLK) on the first postoperative day. (A) An eye with grade 1 DLK. A faint infiltrate in the cap periphery, especially in the peripheral interface around the small incision (red circle). (B) An eye with stage 2 DLK. Diffuse cellular infiltration in the interface but did not extend beyond the edge of the cap (red circle). (C) An eye with stage 3 DLK. A powdery cellular infiltration of the interface, involving the visual axis with multiple, fine granular collections clumped centrally. (D) With a narrow beam, the slit-lamp image showed a highly reflective structure in interface (arrow).

Nine eyes (7.1%) with stage 1 DLK lost one or two lines of CDVA on the first postoperative day, reaching 20/20 or better at the 1-week visit. Eyes with stage 2 and 3 DLK did not achieve a CDVA of 20/20 on the first postoperative day, with a mean CDVA of 0.07 ± 0.04 logMAR. After intense topical corticosteroid treatment (Table 3), DLK resolved in 132 eyes (95.7%) within 1 week and 3 eyes (2.2%) within 2 weeks postoperatively. The 3 eyes with stage 3 DLK required 1 month of treatment with corticosteroid eye drops.

Stage, Position, and Management of DLK After SMILE

Table 3:

Stage, Position, and Management of DLK After SMILE

Corneal Interface Haze

Grade 0.5 corneal interface haze11 was observed in 15 eyes (0.2%). The haze was noted at 1 week in 4 eyes, 1 month in 3 eyes, 2 months in 3 eyes, 3 months in 2 eyes, and 6 months in 3 eyes. Haze was central in 12 eyes (Figure AB), superotemporal in 2 eyes, and inferotemporal in 1 eye. All cases with interface haze were treated with fluorometholone 0.1% eye drops six times daily for 2 months. Three eyes with haze lost one line of CDVA, whereas 3 eyes lost two lines of CDVA. However, these patients improved to 20/20 after 1 year postoperatively.

Infiltrates

Sterile paracentral interface infiltrates developed in 25 eyes (0.4%), 9 of which were observed at 1 day, 15 at 1 week, and 1 at 1 month postoperatively (Figure AD). Additional antibiotic eye drops were administrated six times per day for 3 to 7 days in these patients. All infiltrates resolved after 1 week of treatment. All eyes with infiltrates achieved a CDVA of 20/20 or better.

Interface Debris/Secretions/Foreign Body

Interface debris or secretions were observed in 19 eyes (0.3%) (Figure AC). These resolved without any additional intervention over a period of 1 week to 1 month. Eleven eyes had small interface foreign bodies (0.2%). The source of these foreign bodies was unknown. All eyes with foreign bodies underwent interface irrigation. One of 11 eyes had interface blood (Figure AE). No surgical intervention was performed. The blood resorbed 1 month after surgery. All eyes achieved a CDVA of 20/20 or better by 3 months.

Striae

Linear flap striae (Figure AF) were observed with slit-lamp examination in 9 cases (0.1%), 5 at 1 day postoperatively and 4 at week 1 postoperatively. The CDVA was unaffected in these eyes.

Corneal Edema

Central corneal edema was detected on slit-lamp examination on the first day after SMILE in 6 eyes (0.1%). The edema resolved after treatment with an increased dose of fluorometholone 0.1% eye drops six times per day for 1 week. All eyes with corneal edema achieved a CDVA of 20/20 or better.

Epithelial Ingrowth

One eye (0.02%) developed epithelial ingrowth in the superonasal cornea after 1 month postoperatively (Figure C, available in the online version of this article). Initial management consisted of prednisolone acetate 1% eye drops four times per day for 1 month. However, the epithelial ingrowth did not resolve. Interface debridement was performed at the postoperative 7-month visit. After the debridement, the patient was treated with prednisolone acetate 1% eye drops four times daily and pranoprofen 0.1% eye drops three times daily for 1 week. Mild corneal haze was observed for 1 week after the surgery (Figure D, available in the online version of this article). The final UDVA and CDVA were 20/12.5 and 20/10, respectively.

Epithelial ingrowth in one eye. (A) Fluid ingress between suction ports of the contact glass and the cornea during the scanning of side cut. (B) The incision was manually created with a surgical blade. (C) Slit-lamp photograph showing epithelial ingrowth in the right eye of one patient. (D) Anterior segment optical coherence tomography showing hyperreflective epithelial nests at the interface. Corneal topography showing (E) focal steepening in keratometry and (F) thickening in pachymetry at the area of ingrowth.

Figure C.

Epithelial ingrowth in one eye. (A) Fluid ingress between suction ports of the contact glass and the cornea during the scanning of side cut. (B) The incision was manually created with a surgical blade. (C) Slit-lamp photograph showing epithelial ingrowth in the right eye of one patient. (D) Anterior segment optical coherence tomography showing hyperreflective epithelial nests at the interface. Corneal topography showing (E) focal steepening in keratometry and (F) thickening in pachymetry at the area of ingrowth.

Slit-lamp photograph showing different progression periods of epithelial ingrowth. (A) Slit-lamp photograph at 1 month after it appeared at postoperative 1 month. (B) Slit-lamp photograph at 3 months after it appeared at postoperative 1 month. (C) Slit-lamp photograph at 7 days after epithelial ingrowth debridement.

Figure D.

Slit-lamp photograph showing different progression periods of epithelial ingrowth. (A) Slit-lamp photograph at 1 month after it appeared at postoperative 1 month. (B) Slit-lamp photograph at 3 months after it appeared at postoperative 1 month. (C) Slit-lamp photograph at 7 days after epithelial ingrowth debridement.

Overall Visual Outcomes

Overall, 308 (71.3%) of 432 eyes had a UDVA of better than 20/25 and 49 (11.3%) eyes lost two or more lines of CDVA on the first day after surgery. By 3 months, 244 eyes (99.1%) had achieved a UDVA of better than 20/25 and 2 eyes (0.9%) had lost two or more lines of CDVA. By 6 months postoperatively, only 1 eye (1%) did not achieve a UDVA of 20/25 as a result of stage 3 DLK, but achieved 20/20 at 12 months. Table 4 summarizes the preoperative and postoperative UDVA, CDVA, and spherical equivalent in cases with or without complications over time. There was a significant difference in UDVA between cases with and without complications at 1 day (P = .009) and 1 month (P = .022) postoperatively. The spherical equivalent in cases without complications was lower than that in cases with complications at 1 day, 1 month, and 3 months (P = .001, .011, and .001, respectively). However, there was no statistical difference at 6 and 12 months (P = .980 and .952), as shown in Table 4.

Preoperative and Postoperative Visual Acuity in Cases With and Without Postoperative Corneal Complications

Table 4:

Preoperative and Postoperative Visual Acuity in Cases With and Without Postoperative Corneal Complications

Discussion

Of the 6,373 cases included in this study, 432 eyes (6.78%) developed at least one postoperative complication. Punctate epithelial erosions were the most commonly seen complication, most of which resolved with the use of lubricating eye drops. Sauvageot et al.12 reported a similar incidence of positive fluorescein staining at 1 month after SMILE and FS-LASIK. However, a meta-analysis revealed that the SMILE procedure was associated with lesser impacts on the corneal innervation compared to FS-LASIK, thereby reducing the risk of postoperative dry eyes.13 This may be attributed to the fact that, contrary to LASIK, SMILE does not involve excimer laser photoablation or a full flap cut and therefore has less impact on corneal innervation.14 Previous studies demonstrated that corneal sensitivity after SMILE does not change remarkably.15

The overall incidence of DLK in our cohort was 2.17%, which is similar to that reported in a previous study about DLK after SMILE16 but lower than that reported after FS-LASIK.17,18 In the current study, DLK mostly occurred near the corneal incision on the first day postoperatively, and most cases were stage 1 or 2. All cases responded to treatment with topical corticosteroid eye drops. As compared to LASIK, DLK after SMILE was characterized by (1) faint infiltrates in the periphery, especially close to the incision; (2) short recovery time; and (3) stage 1 or 2 inflammatory response. This may be due to a low pulse energy of the femtosecond laser in SMILE, which results in a less prominent cellular inflammatory response.19 Dong et al.19 and Xia et al.20 showed that SMILE induces less keratocyte apoptosis, proliferation, and inflammation than FS-LASIK. The lower incidence of DLK after SMILE may also be due to the absence of exposure of the stromal bed to the air during surgery. Like LASIK, DLK after SMILE may be related to bacterial endotoxins, debris, Meibomian gland secretions, peripheral immune infiltrates, and epithelial defects.16,21 With timely diagnosis and appropriate aggressive management, the prognosis for DLK after SMILE is good and the refractive outcomes (UDVA, CDVA, and refractive error) were comparable with those without DLK.

Much like LASIK, interface debris or foreign bodies can be seen after SMILE. These are usually small refractile bodies from surgical instrumentation,22,23 corneal epithelium, Meibomian gland secretions, or powder from gloves.24 If the area of debris or foreign bodies is large enough to affect visual acuity or if it causes inflammation, interface irrigation should be performed in the first few days after surgery. In our study, all such cases were successfully managed and achieved good visual outcomes.

Corneal interface haze is another postoperative complication seen after corneal refractive surgery. The overall incidence was 0.24% in the current study, which was lower than in a study on the safety of SMILE by Ivarsen et al.25 We observed that most eyes with corneal haze in our study were reported in the first 100 SMILE procedures, which could be explained by the learning curve of SMILE that may be associated with an excessive manipulation. Further, it may be closely related to the aggressive postoperative flushing of the interface in the initial cases. In the current study, interface irrigation was limited to the incision site in the subsequent cases, which helped reduce the incidence of corneal haze. Transitory haze26 was observed in only 12 eyes in the study, which was noted between 1 and 3 months postoperatively and was visually insignificant. Three eyes developed late haze,26 which appeared at 6 months postoperatively and compromised vision temporarily. The corneal haze responded to medical management with topical corticosteroid eye drops in all cases.

The incidence of corneal striae in our study was lower than that reported in the previous studies.27,28 This was related to our surgical technique, as explained by Yao et al.27 The striae recovered at 1 week, which indicated that the striae in some of these cases were related to the interface space between the stromal bed and the overlying cornea. The cap settles down in the postoperative period, leading to resolution of corneal striae.

We noted only one case with epithelial ingrowth after surgery in our study. The overall incidence was less compared to LASIK.29 We hypothesize that this is due to a small window of stromal access in SMILE.29 We recommend that surgeons should pay special attention to the technique of lenticule dissection during the SMILE procedure and avoid excessive manual dissection. The interface should be carefully examined at the end of the surgery. The timing of surgical intervention depends on the location and size of the epithelial growth and the visual acuity of the patient. Because the patient's visual acuity in our study was not affected initially, we chose to observe the epithelial ingrowth. However, it was finally removed surgically once the patient was symptomatic. The patient's final visual acuity was 20/20 and the mild residual corneal haze dissipated over time.

Although we did not encounter other complications in our study, Zheng et al.30 and Liang et al.31 reported two cases of interface fluid syndrome following SMILE. It is critical to be aware that SMILE may cause interface fluid syndrome and that appropriate intraocular pressure management is an effective approach. Another sight-threatening complication is infection after SMILE. Chehaibou et al.32 described a patient with severe bilateral infectious keratitis after SMILE. The authors suggested strict aseptic precautions in bilateral ocular surgeries, such as SMILE, to prevent cross-contamination. Broad-spectrum antibiotic eye drops are recommended for 3 to 7 days postoperatively.

We observed a multitude of corneal complications after SMILE in this large cohort. Fortunately, most of these complications were mild or transient and responded to conservative management techniques. None of these problems resulted in permanent visual loss in any of our patients. We recommend that surgeons performing SMILE should be aware of these complications. Timely recognition and prompt management of these complications result in good surgical and visual outcomes.

References

  1. 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]
  2. Shah R, Shah S, Sengupta S. Results of small incision lenticule extraction: all-in-one femtosecond laser refractive surgery. J Cataract Refract Surg. 2011;37:127–137. doi:10.1016/j.jcrs.2010.07.033 [CrossRef]
  3. Kamiya K, Shimizu K, Igarashi A, Kobashi H. Visual and refractive outcomes of small incision lenticule extraction for the correction of myopia: 1-year follow-up. BMJ Open. 2015;5:e008268. doi:10.1136/bmjopen-2015-008268 [CrossRef]
  4. Blum M, Taubig 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]
  5. 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]
  6. 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]
  7. Lee JK, Chuck RS, Park CY. Femtosecond laser refractive surgery: small-incision lenticule extraction vs. femtosecond laser-assisted LASIK. Curr Opin Ophthalmol. 2015;26:260–264. doi:10.1097/ICU.0000000000000158 [CrossRef]
  8. Romero-Diaz-de-Leon L, Serna-Ojeda JC, Navas A, Graue-Hernández EO, Ramirez-Miranda A. Intraoperative flap complications in LASIK surgery performed by ophthalmology residents. J Ophthalmic Vis Res. 2016;11:263–267. doi:10.4103/2008-322X.188393 [CrossRef]
  9. dos Santos AM, Torricelli AA, Marino GK, et al. Femtosecond laser-assisted LASIK flap complications. J Refract Surg. 2016;32:52–59. doi:10.3928/1081597X-20151119-01 [CrossRef]
  10. Linebarger EJ, Hardten DR, Lindstrom RL. Diffuse lamellar keratitis: diagnosis and management. J Cataract Refract Surg. 2000;26:1072–1077. doi:10.1016/S0886-3350(00)00468-5 [CrossRef]
  11. Fantes FE, Hanna KD, Waring GO 3rd, Pouliquen Y, Thompson KP, Savoldelli M. Wound healing after excimer laser keratomileusis (photorefractive keratectomy) in monkeys. Arch Ophthalmol. 1990;108:665–675. doi:10.1001/archopht.1990.01070070051034 [CrossRef]
  12. Sauvageot P, Julio G, Alvarez de Toledo J, Chareoenrook V, Barraquer RI. Femtosecond laser-assisted laser in situ keratomileusis versus photorefractive keratectomy: effect on ocular surface condition. J Cataract Refract Surg. 2017;43:167–173. doi:10.1016/j.jcrs.2016.12.019 [CrossRef]
  13. Kobashi H, Kamiya K, Shimizu K. Dry eye after small incision lenticule extraction and femtosecond laser-assisted LASIK: meta-analysis. Cornea. 2017;36:85–91. doi:10.1097/ICO.0000000000000999 [CrossRef]
  14. Behrens A, Doyle JJ, Stern L, et al. Dysfunctional tear syndrome: a Delphi approach to treatment recommendations. Cornea. 2006;25:900–907. doi:10.1097/01.ico.0000214802.40313.fa [CrossRef]
  15. Wei S, Wang Y. Comparison of corneal sensitivity between FSLASIK and femtosecond lenticule extraction (ReLEx flex) or small-incision lenticule extraction (ReLEx smile) for myopic eyes. Graefes Arch Clin Exp Ophthalmol. 2013;251:1645–1654. doi:10.1007/s00417-013-2272-0 [CrossRef]
  16. Zhao J, He L, Yao P, et al. Diffuse lamellar keratitis after small-incision lenticule extraction. J Cataract Refract Surg. 2015;41:400–407. doi:10.1016/j.jcrs.2014.05.041 [CrossRef]
  17. Choe CH, Guss C, Musch DC, Niziol LM, Shtein RM. Incidence of diffuse lamellar keratitis after LASIK with 15 KHz, 30 KHz, and 60 KHz femtosecond laser flap creation. J Cataract Refract Surg. 2010;36:1912–1918. doi:10.1016/j.jcrs.2010.09.003 [CrossRef]
  18. de Paula FH, Khairallah CG, Niziol LM, Musch DC, Shtein RM. Diffuse lamellar keratitis after laser in situ keratomileusis with femtosecond laser flap creation. J Cataract Refract Surg. 2012;38:1014–1019. doi:10.1016/j.jcrs.2011.12.030 [CrossRef]
  19. Dong Z, Zhou X, Wu J, et al. Small incision lenticule extraction (SMILE) and femtosecond laser LASIK: comparison of corneal wound healing and inflammation. Br J Ophthalmol. 2014;98:263–269. doi:10.1136/bjophthalmol-2013-303415 [CrossRef]
  20. Xia L, Zhang J, Wu J, Yu K. Comparison of corneal biological healing after femtosecond LASIK and small incision lenticule extraction procedure. Curr Eye Res. 2016;41:1202–1208. doi:10.3109/02713683.2015.1107590 [CrossRef]
  21. Shah MN, Misra M, Wilhelmus KR, Koch DD. Diffuse lamellar keratitis associated with epithelial defects after laser in situ keratomileusis. J Cataract Refract Surg. 2000;26:1312–1318. doi:10.1016/S0886-3350(00)00570-8 [CrossRef]
  22. Perez-Gomez I, Cameron I, Efron N. Particles at the laser in situ keratomileusis flap interface. J Cataract Refract Surg. 2004;30:2021. doi:10.1016/j.jcrs.2004.06.056 [CrossRef]
  23. Melki SA, Azar DT. LASIK complications: etiology, management, and prevention. Surv Ophthalmol. 2001;46:95–116. doi:10.1016/S0039-6257(01)00254-5 [CrossRef]
  24. Ambrósio R Jr, Wilson SE. Complications of laser in situ keratomileusis. J Refract Surg. 2001;17:350–379.
  25. 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]
  26. Netto MV, Mohan RR, Ambrósio R Jr, Hutcheon AE, Zieske JD, Wilson SE. Wound healing in the cornea: a review of refractive surgery complications and new prospects for therapy. Cornea. 2005;24:509–522. doi:10.1097/01.ico.0000151544.23360.17 [CrossRef]
  27. Yao P, Zhao J, Li M, Shen Y, Dong Z, Zhou X. Microdistortions in Bowman's layer following femtosecond laser small incision lenticule extraction observed by Fourier-domain OCT. J Refract Surg. 2013;29:668–674. doi:10.3928/1081597X-20130806-01 [CrossRef]
  28. Luo J, Yao P, Li M, Zhao J, Tian M, Zhou X. Quantitative analysis of microdistortions in Bowman's layer using optical coherence tomography after SMILE among different myopic corrections. J Refract Surg. 2015;31:104–109. doi:10.3928/1081597X-20150122-05 [CrossRef]
  29. Güell JL, Verdaguer P, Mateu-Figueras G, et al. Epithelial in-growth after LASIK: visual and refractive results after cleaning the interface and suturing the lenticule. Cornea. 2014;33:1046–1050. doi:10.1097/ICO.0000000000000214 [CrossRef]
  30. Zheng K, Han T, Li M, et al. Corneal densitometry changes in a patient with interface fluid syndrome after small incision lenticule extraction. BMC Ophthalmol. 2017;17:34. doi:10.1186/s12886-017-0428-0 [CrossRef]
  31. Liang J, Wang Q, Wang S, Zhang Y. A case of interface fluid syndrome after SMILE. Chin J Optom Ophthalmol Vis Sci. 2017;19:568–571.
  32. Chehaibou I, Sandali O, Ameline B, Bouheraoua N, Borderie V, Laroche L. Bilateral infectious keratitis after small-incision lenticule extraction. J Cataract Refract Surg. 2016;42:626–630. doi:10.1016/j.jcrs.2016.03.024 [CrossRef]

Preoperative Demographics

ParameterMean ± SDRange
Age (years)23 ± 5.4318 to 45
Sex (male/female)1,634/1,58950.7%/49.3%
Sphere (D)−4.93 ± 1.680.00 to −10.00
Cylinder (D)−0.76 ± 0.680.00 to −5.00
Ks (D)43.80 ± 1.4337.80 to 48.00
Kf (D)42.50 ± 1.2837.10 to 46.70
CCT (µm)553 ± 27.93480 to 687
IOP (mm Hg)15.7 ± 2.498.5 to 21

Corneal Complications After SMILE

ComplicationEyes, n (%)Incidence
Punctate epithelial erosions208 (48.15%)3.26%
DLK138 (31.94%)2.17%
Infiltrates25 (5.79%)0.39%
Interface debris/secretion19 (4.40%)0.30%
Interface foreign body11 (2.55%)0.17%
Corneal interface haze15 (3.47%)0.24%
Striae9 (2.08%)0.14%
Corneal edema6 (1.39%)0.09%
Epithelial ingrowth1 (0.23%)0.02%
Interface fluid syndrome00
Infection00

Stage, Position, and Management of DLK After SMILE

StageN (%)Position (n, %)ManagementOutcome
1126 (91.30%)Incision (121, 87.68%); center (1, 0.72%); inferior (4, 2.90%)Normal drug use (78, 61.90%); fluorometholone 0.1% was administered 6 times per day and continued until 1-week visit (48, 38.10%)Disappeared within 1 week
29 (6.52%)Incision (5, 3.63%); center (3, 2.18%); superior temporal (1, 0.72%)Fluorometholone 0.1% was administered 6 times per day and continued until 1-week visitDisappeared within 1 week (6, 66.67%) and 2 weeks (3, 33.33%)
33 (2.18%)Incision (2, 1.45%); center (1, 0.72%)Fluorometholone 0.1% was administered 6 times per day and continued until 1-month visitDisappeared after 1 month

Preoperative and Postoperative Visual Acuity in Cases With and Without Postoperative Corneal Complications

ParameterNo ComplicationsComplicationsP


Mean ± SDnMean ± SDn
UDVA (logMAR)
  Preop1.08 ± 0.355,9391.09 ± 0.39434.544
  Postop 1 d0.01 ± 0.075,8930.02 ± 0.09434.009a
  Postop 7 d−0.03 ± 0.075,405−0.02 ± 0.07409.168
  Postop 1 mo−0.04 ± 0.064,669−0.03 ± 0.06351.022b
  Postop 3 mo−0.05 ± 0.072,986−0.04 ± 0.07246.129
  Postop 6 mo−0.05 ± 0.071,192−0.04 ± 0.08101.211
  Postop 12 mo−0.04 ± 0.07501−0.04 ± 0.0788.896
CDVA (logMAR)
  Preop0.00 ± 0.025,9390.00 ± 0.03434.256
  Postop 1 d−0.06 ± 0.095,893−0.05 ± 0.10434.047b
  Postop 7 d−0.11 ± 0.085,405−0.10 ± 0.08409.233
  Postop 1 mo−0.12 ± 0.084,669−0.11 ± 0.09351.092
  Postop 3 mo−0.12 ± 0.092,986−0.12 ± 0.09246.635
  Postop 6 mo−0.13 ± 0.091,192−0.12 ± 0.09101.766
  Postop 12 mo−0.11 ± 0.08501−0.10 ± 0.0988.454
SE (D)
  Preop−5.40 ± 1.715,939−5.50 ± 1.74434.069
  Postop 1 d−0.31 ± 0.385,893−0.24 ± 0.37434.001a
  Postop 7 d−0.18 ± 0.325,405−0.15 ± 0.32409.112
  Postop 1 mo−0.23 ± 0.384,669−0.17 ± 0.34351.011b
  Postop 3 mo−0.24 ± 0.372,986−0.16 ± 0.32246.001a
  Postop 6 mo−0.17 ± 0.321,192−0.17 ± 0.32101.980
  Postop 12 mo−0.17 ± 0.30501−0.17 ± 0.2788.952
Authors

From the Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China (YW, JM, LZ, HZ, JL, YZ); Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Nankai University, Tianjin Medical University, Tianjin, China (YW, LZ); and UPMC Eye Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania (VJ).

Supported by the National Natural Science Foundation of China (Grant No. 81670884) and Tianjin National Natural Science Foundation (Grant No. 16JCQNJC12600).

The authors have no financial or proprietary interest in the materials presented herein.

Drs. Wang and Ma contributed equally to this work and should be considered as equal first authors.

AUTHOR CONTRIBUTIONS

Study concept and design (YW, JM, VJ); data collection (YW, JM, LZ, HZ, JL, YZ); analysis and interpretation of data (YW, JM); writing the manuscript (YW, JM, LZ, HZ, JL, YZ); critical revision of the manuscript (YW, JM, VJ); statistical expertise (JM); administrative, technical, or material support (YW); supervision (YW, JM, VJ)

Correspondence: Yan Wang, MD, PhD, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Nankai University, Tianjin Medical University, Tianjin, China. E-mail: wangyan7143@vip.sina.com

Received: September 26, 2018
Accepted: January 14, 2019

10.3928/1081597X-20190118-02

Sign up to receive

Journal E-contents