Small incision lenticule extraction (SMILE) has proven to be a safe and efficacious procedure to treat myopia and myopic astigmatism with good safety and stability data up to 10 years.1–3 Similar to laser in situ keratomileusis (LASIK), there remains a low re-treatment rate (1% to 4%).3 Unlike LASIK, enhancements after SMILE require a different surgical procedure for re-treatment, either surface ablation (photorefractive keratectomy [PRK]), thin flap LASIK within the stromal cap, or a cap-to-flap conversion procedure (CIRCLE).3–5
One of the potential challenges with the SMILE procedure is the lack of automated centration, which is currently available on most excimer laser platforms. This increases the risk of treatment decentration if the surgeon is not diligent in using visual cues to confirm a well-centered eye after suction has been established prior to lenticule creation.6–8 Although often asymptomatic for small decentrations, a decentered optical zone can result in visual aberrations, irregular astigmatism with symptomatic blur, reduced quality of vision, and monocular diplopia.7–9
Topography-guided custom ablation treatment (T-CAT) was recently approved by the U.S. Food and Drug Administration for use with the Alcon Wave-Light excimer laser system (Alcon Laboratories, Inc) in the United States for the treatment of myopia and myopic astigmatism,10 and results for primary treatments have been excellent.10–12 Topography-guided ablations using different excimer laser systems have also been used to repair irregular ablations with varying degrees of success.9,13–15 To date, we are not aware of any reports of using the Alcon T-CAT platform to repair decentered ablations induced by SMILE.
The purpose of this report is to present intraoperative visual cues for the identification of a decentered applanation and describe the successful re-treatment after decentered SMILE using T-CAT PRK.
Institutional review approval for this report was granted by the Cleveland Clinic Foundation. A 41-year-old woman presented to a different surgeon seeking consultation for laser vision correction. Corrected distance visual acuity (CDVA) was 20/12 in both eyes with manifest refraction of −6.00 +0.75 × 104° in the right eye and −6.25 +0.50 × 81° in the left eye. Pre-operative Scheimpflug tomography was unremarkable in either eye. Slit-lamp examination was notable for a superficial corneal scar in the right eye and was unremarkable in the left eye. The patient was deemed to be a candidate for refractive surgery and underwent LASIK in the right eye (goal plano), presumably due to the presence of the small stromal scar, and SMILE in the left eye (goal −0.75 diopters [D] sphere).
Per the operative report, planned SMILE treatment for the left eye using the VisuMax laser (Carl Zeiss Meditec) was −5.50 +0.75 × 81° with a 7.5-mm cap diameter, 120 µm cap thickness, 90° side cut angle, 90° incision position, 60° incision angle, 3.93 mm incision width, 6.5 mm optical zone with 0.5 mm transition zone, and lenticule thickness ranging from 15 to 101 µm. Surgery was reportedly uneventful in both eyes.
At 3 months postoperatively, the patient presented to our clinic complaining of blurred vision in the left eye. Uncorrected distance visual acuity (UDVA) was 20/12 in the right eye and 20/50−2, J3 in the left eye. She was completely satisfied with her vision in the right eye after LASIK but noted “blur and strain” along with frank monocular diplopia with ghosting of images in the left eye. On Scheimpflug tomography, she was noted to have a myopic ablation pattern decentered approximately 1.5 mm superiorly on topography in the left eye (Figure A, available in the online version of this article, and Figure 1). Anterior segment optical coherence tomography imaging showed no retained lenticule and a regular epithelial remodeling response to surgery without significant irregularity.
Scheimpflug four-map refractive image of the left eye after small incision lenticule extraction. The point of maximal flattening on anterior curvature, maximum depression on anterior elevation, and minimal thickness values (corresponding to maximal lenticule thickness region) is decentered superiorly. D = diopters
Scheimpflug difference map comparing anterior curvature before (middle image) and after (left image) small incision lenticule extraction (SMILE), with the difference in tangential curvature induced by lenticule extraction shown in the right image. This shows the maximal change in curvature occurred approximately 1.5 mm superior to the patient's optical zone. D = diopters
On retrospective review of the video recording of the surgical procedure, it was evident from the time of suction that there was decentration of the VisuMax patient interface applanation process with the surface of the eye and this decentration was maintained throughout lenticule creation (Figure 2) (Video 1 and Figure B, available in the online version of this article).
(A) Preoperative topography raw image map, inverted to match the surgeon's view, and intraoperative images (surgeon's view) during (B) docking and (C) lenticule creation, demonstrating superior decentration during lenticule creation. Figure 2A shows the location of the patient's visual axis marked as the intersection of the two yellow lines; when comparing this to the green fixation light in Figure 2B, there is a clear superior decentration and a notable decentration relative to the pupil as shown in the relative difference in distance between the green centration dot and the pupil edge (white arrow), and suction ring placement beyond the limbus as seen superiorly (black arrow). In Figure 2C, at the initiation of laser treatment decentration is again detectible, as the pupil edge is obscured inferiorly but still visible superiorly (black arrow).
Intraoperative image obtained after lenticule creation but before lenticule dissection. The corneal suction pattern is still apparent at this juncture and is visible in the peripheral cornea inferiorly (black arrow) but extends well beyond the limbus onto the sclera superiorly (black arrow). Although the limbus is not an accurate determinant of the visual axis, this level of suction fixation decentration should alert the surgeon to confirm that the created lenticule was in fact centered, because this is the last opportunity to do so prior to lenticule removal.
The patient's visual symptoms persisted without change postoperatively. At postoperative month 6, with stable refractive and tomographic evaluation, it was deemed appropriate to pursue retreatment. At this time, manifest refraction in the right (LASIK) eye was plano (goal plano), whereas the affected left (SMILE) eye was −0.50 −0.50 × 001° (goal −0.75 sphere) with monocular diplopia that was not alleviated with spectacle correction. After discussing risks, benefits, and treatment options, the decision was made to proceed with T-CAT PRK with a goal of plano.
The Alcon Topolyzer VARIO system was used to plan the T-CAT PRK treatment using a final treatment refraction of −0.38 −0.75 × 5°; the aberration-only ablation pattern, shown in the treatment planning phase, mirrored the patient's irregular topography (Figure 3). Manual epithelial debridement was performed following ethanol application for 30 seconds. The ablation was applied after successful pupil recognition and optimal centration was confirmed. Following ablation, mitomycin C was applied for 60 seconds and a bandage contact lens was placed at the end of the case. Topical antibiotic (moxifloxacin 0.5%) was applied at the end of the case and used three times daily for 1 week, and a topical steroid (0.1% prednisolone acetate) was used four times daily for the first 2 weeks and then tapered over the course of 6 weeks postoperatively.
Composite image showing Scheimpflug anterior curvature map (left) and the planned topography-guided custom ablation treatment (T-CAT) ablation pattern showing only corneal aberration treatment (right). There is a distinct correlation between the region of maximal planned ablation related to aberrations (approximately 20 µm) in the T-CAT image that is located superiorly and inferiorly to the region of maximal flattening (maximal small incision lenticule extraction lenticule thickness) in Scheimpflug curvature image. D = diopters
At postoperative month 1, UDVA was 20/12 with a manifest refraction of −0.25 D sphere in the re-treated eye. There was complete subjective resolution of diplopia symptoms, improved ablation zone centration (Figure C, available in the online version of this article, and Figure 4), and a decrease in corneal higher order aberrations, most notably vertical coma (−0.65 µm after SMILE to 0.197 µm after T-CAT PRK). The patient remined stable through 12 months of follow-up and was satisfied with her final visual acuity.
Scheimpflug four map refractive image of the left eye after topography-guided custom ablation treatment photorefractive keratectomy. The point of maximal flattening on anterior curvature is now located centrally, indicating that optical zone recentration has been successful. D = diopters
Scheimpflug difference map comparing anterior curvature after small incision lenticule extraction (SMILE) (middle image) and after topography-guided custom ablation treatment photorefractive keratectomy (T-CAT PRK) (left image), with the difference in curvature induced by lenticule extraction shown in the right image. This demonstrates the selective change in curvature induced by T-CAT PRK and the resulting improved optical zone centration. D = diopters
This case demonstrates the ability of T-CAT PRK to correct irregular astigmatism induced by decentered SMILE lenticule creation and highlights the need for surgeon diligence intraoperatively to minimize the risk of visually significant decentration at the time of SMILE.
SMILE decentration typically does not result in reduced visual quality. Dishler et al6 reported five cases with SMILE decentration with no loss of visual acuity or unwanted visual symptoms resulting in any case. The degree of decentration in our patient resulted in decreased visual acuity, increased higher order aberrations, and symptomatic monocular diplopia. A significant relationship has been reported between the magnitude of decentration and 3-month postoperative corneal higher order aberrations, especially if the total decentered displacement is greater than 0.335 mm.7 Although the risk of decentration has been reported to be similar to that for LASIK for experienced surgeons,16,17 there are additional intraoperative challenges to obtaining and confirming treatment centration with SMILE due to the lack of automated centration systems that are present on modern excimer lasers. Treatment centration with SMILE is directly related to surgical technique and therefore the risk of clinically significant decentration is greater for less experienced surgeons.18 In our retrospective case review, the decentered applanation process was subtle but evident from the initiation of suction and at various time points during the procedure (Figure 3). The best course of action would have been to redock or abort the procedure if these signs had been identified at the time of surgery.
There are a variety of techniques proposed to facilitate SMILE centration.19,20 Liu et al20 recently reported improved treatment centration and less induction of total higher order aberrations (including vertical and horizontal coma and spherical aberrations) when treatment was centered on the applanated tear film meniscus rather than the pupil center. Reinstein et al16 described the use of the raw capture image from a preoperative topographic map (inverted to match the surgeon's view) to facilitate identification of the location of the visual axis within the pupillary borders as another method to confirm centration prior to lenticule creation.
Topography-guided excimer laser ablation can address irregularities in corneal topography in an effort to minimize astigmatism and aberrations at the level of the cornea while correcting the patient's manifest refractive error.10–12 T-CAT PRK has also been found to be efficacious as a primary refractive treatment.21 Although approved for treatment of virgin eyes, the use of T-CAT PRK for the treatment of irregular astigmatism remains an off-label procedure in the United States. There are likely differences in the software approvals and parameters that can be modified for T-CAT ablations between what is available within and outside the United States, so users from other countries should familiarize themselves with the full functionality of the device where they practice when planning for topography-guided treatments.
Ivarsen and Hjortdal9 presented a series of 5 eyes that underwent topography-guided PRK for irregular astigmatism after complicated SMILE cases using the MEL-80 excimer laser (Carl Zeiss Meditec). In most of these eyes, perioperative complications during lenticule extraction had been documented, and in all cases irregular Bowman's layer with compensatory epithelial hyperplasia was noted postoperatively. This cohort experienced variable degrees of improvement in subjective symptoms, UDVA, CDVA, and corneal wavefront aberrations in 3 eyes, whereas the remaining 2 eyes developed significant postoperative haze with decreased CDVA. The eyes that developed haze were not treated with mitomycin C.9 Siedlecki et al4 reported in a series of 43 eyes that SMILE re-treatment with topography-guided, triple-A, or tissue-saving algorithms for PRK were safe when combined with the intraoperative application of mitomycin C but reported overcorrection with the aspherically optimized profile they used. Our patient was treated with mitomycin C at the time of re-treatment and developed no significant corneal haze throughout 12 months of follow-up. It is possible that previous case complications with lenticule extraction predisposed the cases reported by Ivarsen and Hjortdal9 to develop haze, whereas there were no intraoperative issues with any step of the procedure in this case, including lenticule extraction, except for the decentered treatment identified postoperatively.
T-CAT PRK using the Alcon EX500 excimer laser with mitomycin C was efficacious for re-treatment following decentered SMILE and resulted in an excellent refractive outcome, decrease in higher order aberrations, and resolution of subjective visual symptoms. Diligence is required to avoid SMILE treatment decentration and special attention to visual cues can minimize this complication. T-CAT PRK can be a useful tool to correct irregular astigmatism when used in the proper setting and can be considered as a therapeutic modality for cases of decentered SMILE treatments.
- Blum M, Lauer AS, Kunert KS, Sekundo W. 10-year results of small incision lenticule extraction. J Refract Surg. 2019;35(10):618–623. doi:10.3928/1081597X-20190826-02 [CrossRef]
- Ang M, Farook M, Htoon HM, Mehta JS. Randomized clinical trial comparing femtosecond LASIK and small-incision lenticule extraction. Ophthalmology. 2020;127(6):724–730. doi:10.1016/j.ophtha.2019.09.006 [CrossRef]
- Moshirfar M, Shah TJ, Masud M, Linn SH, Ronquillo Y, Hoopes PC Sr, . Surgical options for re-treatment after small-incision lenticule extraction: advantages and disadvantages. J Cataract Refract Surg. 2018;44(11):1384–1389. doi:10.1016/j.jcrs.2018.07.047 [CrossRef]
- Siedlecki J, Luft N, Kook D, et al. Enhancement after myopic small incision lenticule extraction (SMILE) using surface ablation. J Refract Surg. 2017;33(8):513–518. doi:10.3928/1081597X-20170602-01 [CrossRef]
- Siedlecki J, Siedlecki M, Luft N, et al. Surface ablation versus CIRCLE for myopic enhancement after SMILE: a matched comparative study. J Refract Surg. 2019;35(5):294–300. doi:10.3928/1081597X-20190416-02 [CrossRef]
- Dishler JG, Slade S, Seifert S, Schallhorn SC. Small-incision lenticule extraction (SMILE) for the correction of myopia with astigmatism: outcomes of the United States Food and Drug Administration Premarket Approval Clinical Trial. Ophthalmology. 2020;127(8):1020–1034. doi:10.1016/j.ophtha.2020.01.010 [CrossRef]
- Lee H, Roberts CJ, Arba-Mosquera S, Kang DSY, Reinstein DZ, Kim TI. Relationship between decentration and induced corneal higher-order aberrations following small-incision lenticule extraction procedure. Invest Ophthalmol Vis Sci. 2018;59(6):2316–2324. doi:10.1167/iovs.17-23451 [CrossRef]
- Liu M, Sun Y, Wang D, et al. Decentration of optical zone center and its impact on visual outcomes following SMILE. Cornea. 2015;34(4):392–397. doi:10.1097/ICO.0000000000000383 [CrossRef]
- Ivarsen A, Hjortdal JØ. Topography-guided photorefractive keratectomy for irregular astigmatism after small incision lenticule extraction. J Refract Surg. 2014;30(6):429–432. doi:10.3928/1081597X-20140508-02 [CrossRef]
- Stulting RD, Fant BS, Bond W, et al. T-CAT Study Group. Results of topography-guided laser in situ keratomileusis custom ablation treatment with a refractive excimer laser. J Cataract Refract Surg. 2016;42(1):11–18. doi:10.1016/j.jcrs.2015.08.016 [CrossRef]
- Wallerstein A, Gauvin M, Qi SR, Bashour M, Cohen M. Primary topography-guided LASIK: treating manifest refractive astigmatism versus topography-measured anterior corneal astigmatism. J Refract Surg. 2019;35(1):15–23. doi:10.3928/1081597X-20181113-01 [CrossRef]
- Wallerstein A, Caron-Cantin M, Gauvin M, Adiguzel E, Cohen M. Primary topography-guided LASIK: refractive, visual, and subjective quality of vision outcomes for astigmatism ≥2.00 diopters. J Refract Surg. 2019;35(2):78–86. doi:10.3928/1081597X-20181210-01 [CrossRef]
- Jankov MR II, Panagopoulou SI, Tsiklis NS, Hajitanasis GC, Aslanides M, Pallikaris G. Topography-guided treatment of irregular astigmatism with the wavelight excimer laser. J Refract Surg. 2006;22(4):335–344. doi:10.3928/1081-597X-20060401-07 [CrossRef]
- Ghoreishi M, Naderi Beni A, Naderi Beni Z. Visual outcomes of topography-guided excimer laser surgery for treatment of patients with irregular astigmatism. Lasers Med Sci. 2014;29(1):105–111. doi:10.1007/s10103-013-1282-9 [CrossRef]
- Reinstein DZ, Gobbe M, Archer TJ, Youssefi G, Sutton HF. Stromal surface topography-guided custom ablation as a repair tool for corneal irregular astigmatism. J Refract Surg. 2015;31(1):54–59. doi:10.3928/1081597X-20141218-06 [CrossRef]
- Reinstein DZ, Gobbe M, Gobbe L, Archer TJ, Carp GI. Optical zone centration accuracy using corneal fixation-based smile compared to eye tracker-based femtosecond laser-assisted LASIK for myopia. J Refract Surg. 2015;31(9):586–592. doi:10.3928/1081597X-20150820-03 [CrossRef]
- Damgaard IB, Ang M, Mahmoud AM, Farook M, Roberts CJ, Mehta JS. Functional optical zone and centration following SMILE and LASIK: a prospective, randomized, contralateral eye study. J Refract Surg. 2019;35(4):230–237. doi:10.3928/1081597X-20190313-01 [CrossRef]
- Li M, Zhao J, Miao H, et al. Mild decentration measured by a Scheimpflug camera and its impact on visual quality following SMILE in the early learning curve. Invest Ophthalmol Vis Sci. 2014;55(6):3886–3892. doi:10.1167/iovs.13-13714 [CrossRef]
- Kang DSY, Lee H, Reinstein DZ, et al. Comparison of the distribution of lenticule decentration following SMILE by subjective patient fixation or triple marking centration. J Refract Surg. 2018;34(7):446–452. doi:10.3928/1081597X-20180517-02 [CrossRef]
- Liu S, Zhang X, You Z, Zhou X. Comparison of the distribution of lenticule decentration following SMILE by pupil center or tear film mark centration. J Refract Surg. 2020;36(4):239–246. doi:10.3928/1081597X-20200310-01 [CrossRef]
- Faria-Correia F, Ribeiro S, Monteiro T, Lopes BT, Salomão MQ, Ambrósio R Jr, . Topography-guided custom photorefractive keratectomy for myopia in primary eyes with the WaveLight EX500 platform. J Refract Surg. 2018;34(8):541–546. doi:10.3928/1081597X-20180705-03 [CrossRef]