EyeWorld Asia-Pacific September 2016 Issue

September 2016 EWAP FEATURE 27 Views from Asia-Pacific Rick WOLFE, MD Medical Director, Peninsula Eye Centre 937 Nepean Hwy, Mornington VIC 3931, Australia Tel. no. +61-3-5975-9999 Fax no. +61-3-5975-9899 rwolfe@vistaeyes.com.au T he article is filled with enthusiasm and hope that SMILE might one day show some material advantage over LASIK. I understand that SMILE surgeons have an enormous financial, professional, and personal investment in this novel and most interesting procedure. It must, then, not fill them with hope when, after all this time, the best that can be said in the article, in a truly evidence-based way, is “A recent meta-analysis 1 found SMILE and femtosecond LASIK were comparable in terms of safety and efficacy…”
. The claims of better vision made in the article are not substantiated. Published studies have not yet compared SMILE with the best of wavefront-guided (WFG) or topographic-guided (TG) LASIK. However, there very recently has appeared a comparative study 2 of LASIK, WFG LASIK, and femtosecond lenticule extraction FLEx (a procedure closely related to SMILE with removal of the same lenticule with the femtosecond laser, but from under a flap rather than a cap). One might expect similar optical results with FLEx and SMILE because the refractive component is produced in exactly the same way. The study showed that, compared with FLEx, WFG LASIK is associated with: • less higher order aberration (HOA) induction • better mesopic contrast sensitivity with and without glare • lower surface regularity index (SRI) and • lower surface asymmetry index (SAI) than FLEx. The authors propose mechanisms for how the less regular surface after FLEx might relate to the femtosecond laser cuts. A recently published study of TG LASIK, 3, 4 whilst admittedly not comparative, has shown better visual and aberrometric outcomes than SMILE studies. SMILE certainly eliminates the less efficient peripheral excimer ablation in myopic treatments, thereby causing very little induced spherical aberration. TG LASIK can actually eliminate spherical aberration induction completely, whilst providing truly excellent HOA and visual results. Advanced ablation profiles, such as TG must represent the future. SMILE probably cannot participate in such advanced ablation profiles, which take into account preexisting HOAs. The femtosecond laser lacks the submicron axial precision of the excimer laser. Of real concern are Bowman’s membrane distortions seen in the SMILE cap on OCT. In one series, these occurred in 60% of cases and were responsible for poorer retinal image quality and retinal light scatter. Perhaps a different manifestation of the same pathology is the Bowman’s membrane striae, visible when the epithelium is removed for PRK enhancement of SMILE. Visual recovery can be very slow in SMILE. It can take 6 months to achieve LASIK-like results, reducing the “wow” factor. How many patients want to wait this long? This possibly presents the biggest barrier to patient and doctor acceptance of SMILE. The hope that the theoretical biomechanical advantage of SMILE might prevent ectasia perhaps should be abandoned with the recent publication of seven cases of ectasia after SMILE. Not all cases had abnormal topography. Randleman 6 , in his recent Journal of Refractive Surgery editorial, called for caution in proceeding with SMILE because of these cases. I think the two major factors that favor a future for SMILE are the elimination of potential late flap dislocation, infrequently seen in LASIK and an, as it appears, incorrect patient perception of less invasiveness and greater safety. The article’s promise, “…it’s going to get better,” is reassuring and shows the contributors still have hope. “Hope springs eternal…” References 1. Zhang Y, et al. Clinical outcomes of SMILE and FS-LASIK used to treat myopia: a meta-analysis. J Refract Surg . 2016;32:256–65. 2. Zheng Y, et al. Comparison of Visual Outcomes After Femtosecond LASIK, Wave Front-Guided Femtosecond LASIK, and Femtosecond Lenticule Extraction. Cornea . 2016;35:1057–1061 3. T-CAT-001 study. PMA P020050/S12: FDA Summary of Safety and Effectiveness Data. Available at www.fda.gov Accessed 15 Jun 16. 4. Stulting RD, Fant BS, the 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;42:11–18. 5. Shetty R, Shroff R, Kaweri L, Jayadev C, Kummelil MK, Sinha Roy A. Intra-Operative Cap Repositioning in Small Incision Lenticule Extraction (SMILE) for Enhanced Visual Recovery. Curr Eye Res. 2016 Apr 4:1-7. 6. Randleman B Editorial: Ectasia After Corneal Refractive Surgery: Nothing to SMILE About. J Refract Surg. 2016;32:434-435. Editors’ note: Dr. Wolfe is an investigator for Alcon (Fort Worth, Texas). continued on page 28