EyeWorld Asia-Pacific September 2014 Issue

64 EWAP DEVICES September 2014 Swept-source - from page 63 changes in that area are thought to impede flow within the axons,” said Barry A. Schechter, MD , director of the cornea and cataract service, Florida Eye Microsurgical Institute, Boynton Beach, Fla., U.S. If swept-source OCT can discern details of more deeply located tissues, it might “provide earlier and more detailed views to help clinicians better treat our glaucomatous patients,” he said. In the anterior segment, Dr. Schechter said the technology might prove useful in visualization of synechiae and angle structures. An improved ability to ascertain where microincisional glaucoma surgery devices have been placed is a potential use as well, he said. For now, Dr. Shen said she’s “cautiously optimistic” about the future of swept-source technology. EWAP References 1. Grulkowski I, Liu JJ, Potsaid B, et al. Retinal, anterior segment and full eye imaging using ultrahigh speed swept source OCT with vertical-cavity surface emitting lasers. Biomed Opt Express . 2012;3(11):2733–51. 2. Wang B, Nevins JE, Nadler Z, et al. In vivo lamina cribrosa microarchitecture in healthy and glaucomatous eyes as assessed by optical coherence tomography. Invest Ophthalmol Vis Sci. 2013;54:8270–8274. Editors’ note: Dr. Fujimoto has financial interests with Optovue (Fremont, Calif., U.S.) and Carl Zeiss Meditec (Jena, Germany). Drs. Schechter and Shen have no financial interests related to their comments. None of the swept-source devices mentioned in this article are commercially available in the United States. Contact information Fujimoto: jgfuji@mit.edu Schechter: bdsch77@aol.com Shen: Lucy_Shen@meei.harvard.edu Biomechanics - from page 61 CRF and CH was also examined. A statistically significant correlation was demonstrated between RST index and delta CRF and CH in the lenticule extraction group. In contrast, the correlations were not significant in the femtosecond LASIK group. No explanation was provided for this difference in the discussion, but perhaps with flap creation, corneal biomechanics are no longer as closely integrated to the anterior stroma due to the redistribution of forces elsewhere. With stromal preservation in SMILE, corneal biomechanics may more closely resemble preoperative paradigms. Interestingly, two studies have explicitly sought to examine the change in corneal biomechanical properties following LASIK and PRK. While Hamilton et al. found CH and CRF decreased similarly after PRK and LASIK (both microkeratome and laser-assisted flap creation) when controlling for ablation depth, Kamiya et al. concluded that biomechanical change (CH and CRF) is larger after LASIK (microkeratome). Of note, PRK and LASIK eyes had similar average refractive errors in the later study, but ablation depth was not controlled. Kamiya et al. also did not report any cases of ectasia in the 6-month follow-up period. 10,11 Although case reports have suggested an increased risk of ectasia following LASIK compared with PRK in fellow eyes of the same patients, prospective studies with long-term follow-up are needed to clarify whether this association is more than anecdotal. The removal of corneal stromal tissue in both procedures must weaken the cornea to some degree, and the fact that SMILE seems to alter these properties to a lesser extent is both interesting and promising. Why this delta value only reaches significance for CRF and not CH remains unclear. The real test will be whether results from this investigation pan out long term on a clinical level. If ReLEx SMILE can limit post- refractive surgery ectasia and still achieve an excellent visual outcome, it may inspire a shift in refractive surgery patterns moving forward. EWAP References 1. Blum M, Kunert KS, Vobmerbaumer U, Sekundo W. Femtosecond lenticule extraction (ReLEx) for correction of hyperopia – first results. Graefes Arch Clin Exp Ophthalmol. 2013;1:349–55. 2. Hjortdal JO, Vestergaard AH, Ivarsen A, Ragunathan S, Asp S. Predictors for the outcome of small-incision lenticule extraction for myopia. J Refract Surg. 2012;28:865–71. 3. Vestergaard AH, Gronbech KT, Grauslund J, Ivarsen AR, Hjortdal JO. Subbasal nerve morphology, corneal sensation, and tear film evaluation after refractive femtosecond laser lenticule extraction. Graefes Arch Clin Exp Ophthalmol. 2013;251:2591–600. 4. 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;95:335–9. 5. Hjortdal JO, Vestergaard AH, Ivarsen A, Ragunathan S, Asp S. Predictors for the outcome of small-incision lenticule extraction for myopia. J Refractive Surg. 2012;25:865–71. 6. Vestergaard A, Ivarsen AR, Asp S, Hjortdal JO. Small-incision lenticule extraction for moderate to high myopia: Predictability, safety, and patient satisfaction. J Cataract Refract Surg. 2012;38:2003–10. 7. Kamiya K, Igarashi A, Ishii R, Sato N, Nishimoto H, Shimizu K. Early clinical outcomes, including efficacy and endothelial cell loss of refractive lenticule extraction using a 500 kHz femtosecond laser to correct myopia. J Cataract Refract Surg. 2012;38: 1996–2002. 8. Wu D, et al. Corneal biomechanical effects: Small-incision lenticule extraction versus femtosecond laser- assisted laser in situ keratomileusis. J Cataract Refract Surg . 2014;40:954– 962. 9. Ortiz D, Pinero D, Shabayek MH, Arnalich-Montiel F, Alio JL. Corneal biomechanical properties in normal, post-laser in situ keratomileusis and keratoconic eyes. J Cataract Refract Surg. 2007;33:1371–1375. 10. Hamilton DR, Johnson RD, Lee N, Bouria N. Differences in the corneal biomechanical effects of surface ablation compared with laser in situ keratomileusis using a microkeratome or femtosecond laser. J Cataract Refract Surg. 2008;34:2049–56. 11. Kamiya K, Shimizu K, Ohmoto F. Comparison of the changes in corneal biomechanical properties after photorefractive keratectomy and laser in situ keratomileusis. Cornea. 2009;28:765–9. Contact information Starr: drstarr@gmail.com