EyeWorld Asia-Pacific June 2016 Issue

EWAP SECONDARY FEATURE 29 June 2016 by Gerard Sutton, MBBS, MD, FRANZCO, FRACS SMILE: Personal experience L earning Curve Our center began using the SMILE technique over 12 months ago and I have personally completed between 400-500 eyes in that time. There is no doubt that a surgical learning curve exists for the technique; however, this should not represent a problem for competent refractive or corneal surgeons. Achieving a consistent lenticule removal technique is important, as is ensuring adequate centration, however practically. The essential issue is ensuring that the unit’s energy settings and laser environment are clarified and well-controlled. Our postoperative refractive results were satisfactory from the inception of the laser; however, as we managed to refine the laser energy levels, the lenticule removal became easier and, furthermore, visual recovery appeared significantly faster, now only slightly behind the expected recovery of LASIK. I would strongly advise anyone adopting this technology to ensure strict environmental control of humidity and temperature and that your Zeiss (Jena, Germany) backup technician is experienced in finessing your initial energy and spot size settings. Effective refractive range of SMILE We introduced SMILE to the moderate to high myopes initially (–5 D and above) before expanding the range to mild myopia, with or without astigmatism. The visual and refractive results with higher myopes have been at least as good as those we previously achieved with LASIK, if not better. There does not appear to be any clear peer-reviewed evidence that SMILE currently provides obviously better results than LASIK in low myopia— both are excellent procedures. LASIK is by no means dead. SMILE is however my preferred procedure for myopia –3 to –10 D assuming adequate corneal thickness. Potential advantages of SMILE Current literature suggests that corneal sensitivity is less impacted in SMILE patients. Most studies also show that dry eye is less an issue than in LASIK patients. This is consistent with my experience. Visual recovery remains marginally slower than LASIK; however, the final quality of vision, particularly in the higher myopes, appears to be better. This likely reflects a decrease in the induction of spherical aberration following SMILE in comparison to equivalent LASIK refractive errors. Recent literature supports this assumption. 1 Coma levels remain variable with some studies suggesting that it is higher in the SMILE cohort. I would suggest that this is related to decentration. Centration is an issue. Whilst a decentration may have less impact than a decentration in LASIK, it should not be trivialized. I center on the 1st Purkinje Image and clearly there is subjectivity involved in this decision. Whilst experience improves one’s ability to centrate the treatment, the next iteration of this technology should allow a virtual centration—ieally with preoperative registration. Whislt Zeiss are at it they should also look at narrowing the patient interface which is significantly less user-friendly than either the Intralase or the Lensex in patients with a large proboscis. At 1 year it is difficult to tell from our experience whether the proposed biomechanical advantages of SMILE represent a clinical advantage over LASIK. Blum et al. 2 have now shown no ectasia in their small primary cohort at 5 years; however, ectasia has been reported. 3 This is not a tectonically risk-free procedure. Patients that represent high-risk candidates for LASIK will similarly remain at risk of ectasia in SMILE. SMILE at our practice Over the initial 6 months or so of SMILE, the percentage of patients undergoing this technique was around 20%. This was a reflection of the local patient demographic of high myopes as much as my level of comfort with the procedure. Following this initial period, SMILE has rapidly expanded and is now used in approximately 60% of my myopic patients undergoing laser refractive surgery, more common than either LASIK or PRK. Despite minimal marketing, the majority of patients now arriving for refractive consultation at my practice have knowledge of SMILE and request the procedure if suitable. This has led to an increase in our overall surgical volume. It is likely a combination of factors including both the excitement surrounding “new” technology and the proposed benefits of the procedure itself. I continue to offer LASIK, PRK, and phakic IOLs, and see SMILE as an increasingly suitable choice in my surgical quiver. EWAP References 1. Wu W, Wang Y. Corneal Higher-Order Aberrations of the Anterior Surface, Posterior Surface, and Total Cornea After SMILE, FS-LASIK, and FLEx Surgeries. Eye Contact Lens . 2016 Mar 29. [Epub ahead of print] 2. Blum M, Täubig K, Gruhn C, Sekundo W, Kunert KS. Five-year results of Small Incision Lenticule Extraction (ReLEx SMILE). Br J Ophthalmol . 2016 Jan 8. pii: bjophthalmol-2015-306822. doi: 10.1136/bjophthalmol-2015-306822. [Epub ahead of print] 3. Remy M, Kohnen T. Corneal ectasia after femtosecond laser-assisted small-incision lenticule extraction in eyes with subclinical keratoconus/ forme fruste keratoconus. J Cataract Refract Surg . 2015 Jul;41(7):1551-2. Editors’ note: Dr. Sutton has no relevant financial interests. Gerard Sutton