Ectasia following small-incision lenticule extraction (SMILE): a review of the literature
Authors Moshirfar M, Albarracin JC, Desautels JD, Birdsong OC, Linn SH, Hoopes Sr PC
Received 22 July 2017
Accepted for publication 28 August 2017
Published 15 September 2017 Volume 2017:11 Pages 1683—1688
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 2
Editor who approved publication: Dr Scott Fraser
Majid Moshirfar,1,2 Julio C Albarracin,3 Jordan D Desautels,1,4 Orry C Birdsong,1 Steven H Linn,1 Phillip C Hoopes Sr1
1HDR Research Center, Hoopes Vision, Draper, 2John A Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, 3Department of Ophthalmology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, 4Department of Ophthalmology, Warren Alpert Medical School of Brown University, Providence, RI, USA
Purpose: Four cases of corneal ectasia after small-incision lenticule extraction (SMILE) have been reported. In this review, we provide an overview of the published literature on corneal ectasia after SMILE and risk factors associated with this complication.
Methods: Case reports were identified by a search of seven electronic databases for pertinent heading terms between 2011 and July 2017. We identified patient characteristics and surgical details including preoperative topography, central corneal thickness, and anterior keratometry (Km). Residual stromal bed (RSB) values not reported were computed using VisuMax ReLEx SMILE software Version 2.10.10. Preoperative ectasia risk was measured using the Randleman Ectasia Risk Score System (ERSS). Percent tissue alteration was calculated for each patient as described by Santhiago et al.
Results: Seven eyes of four patients developed corneal ectasia post SMILE. Two patients had abnormal topography in both eyes. One patient had abnormal topography in one eye. Only one patient was noted to have normal topography in both eyes and later developed ectasia in one eye in the absence of any known risk factors. The mean Randleman ectasia risk score was 4±3 (range: 1–8). The mean calculated percent tissue altered (PTA) was 38%±6% (range: 30%–47%).
Conclusion: A majority of reported ectasia cases occurred in patients with subclinical keratoconus. These conditions may be exacerbated by SMILE and should be considered absolute contraindications to the procedure. Three patients were identified to have high risk based on the ERSS, and one patient exhibited a PTA ≥40%. We formulated a modification to the current calculation of PTA that takes into account the differences in tissue altered between SMILE and laser in situ keratomileusis (LASIK). More studies are needed to fully quantify the risk of ectasia. For now, we propose adopting the same exclusion criteria used for LASIK in the SMILE procedure until more specific metrics have been validated.
Keywords: SMILE, small-incision lenticule extraction, ectasia, keratoconus, percent tissue altered, Ectasia Risk Score System
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