EyeWorld Asia-Pacific September 2012 Issue

52 September 2012 EWAP DEVICES Clinical results with this femtosecond laser- based refractive surgery technique T oday, although several sophisticated excimer laser refractive surgeries are available to perform vision correction with high accuracy, a major advancement has been the introduction of the femtosecond (FS) laser, which has thrived during the past decade. The original indication of the FS laser in corneal refractive surgery was primarily flap creation for the LASIK procedure, which has been widely adopted due to its improved safety, predictability and versatility 1,2 . Several studies have been published attesting to the many benefits of FS laser-assisted flap creation over microkeratome- assisted flaps, including stronger adhesion at the flap edge and interface 3 , thin and uniform (planar) flaps 4,5 , enhanced flap biomechanics 6,7 , and fewer induced higher order aberrations 8 . More recently, the FS laser has been used as the sole laser in vision correction procedures, obviating the use of an excimer laser, which marks the beginning of a new era. Flap creation as well as the refractive correction can be performed using the same laser, currently using the VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany), in a procedure called refractive lens exchange (ReLEx), encompassing femtosecond lamellar extraction (FLEx) and small incision lamellar extraction (SMILE). FLEx is similar to LASIK in that a flap is created, and lifted aside. However, the refractive correction is performed with the femtosecond laser to cut a refractive lenticule. Unlike conventional LASIK, the SMILE procedure, which is the logical development of FLEx, does not require a flap. Instead, a small lens-shaped section is created inside the still-intact cornea, which is then removed in one piece through a small incision. Because no flap is created, the biomechanical stability of the cornea remains largely intact. From September 2011, our refractive surgery center at Tianjin Eye Hospital began pioneering work on SMILE surgery in China, and established a training center for ReLEx surgery. We have since successfully finished 103 SMILE surgeries, and achieved satisfying early clinical results. The preoperative manifest refraction spherical equivalent (MRSE) was –5.57±1.21 D, ranging from –3.50 to –8.88 D, and mean sphere ranging from –1.75 to –8.25 D (mean, SD –5.11±1.35 D), as well as mean cylinder ranging from –3.75 to 0.00 D (mean, SD –0.92±0.93 D). A recent publication from Dr. Rupal Shah reports the 6-month outcome of SMILE surgery, revealing a satisfactory result, and concedes that the procedure appears to SMILE for laser vision correction by Wang Yan, MD The stability of the refractive outcome over the 3-month follow-up period. Source: Wang Yan, MD be a safe and promising corneal refractive procedure for correcting myopia 9 . In our clinic, the SMILE procedures were performed successfully in all patients; 89.9% of eyes maintained their CDVA, and 10.1% gained 2 lines at the third month after surgery. No eyes lost CDVA. The residual SEQ was –0.14±0.37 D, the sphere was 0.00±0.41 D, and the astigmatism was –0.29±0.35 D after 3 months. Based on our clinical results with SMILE, the technique provides safe, effective, and predictable results. The flapless SMILE procedure offers clear clinical benefits. EWAP References 1. Stonecipher K, Ignacio TS, Stonecipher M. Advances in refractive surgery: microkeratome and femtosecond laser flap creation in relation to safety, efficacy, predictability, and biomechanical stability. Curr Opin Ophthalmol. 2006 Aug;17(4):368-72. 2. Sutton G, Hodge C. Accuracy and precision of LASIK flap thickness using the IntraLase femtosecond laser in 1000 consecutive cases. J Refract Surg. 2008 Oct;24(8):802-6. 3. Kim JY, Kim MJ, Kim TI, Choi HJ, Pak JH, Tchah H. A femtosecond laser creates a stronger flap than a mechanical microkeratome. Invest Ophthalmol Vis Sci . 2006 Feb;47(2):599-604. 4. Stahl JE, Durrie DS, Schwendeman FJ, Boghossian AJ. Anterior segment OCT analysis of thin IntraLase femtosecond flaps. J Refract Surg . 2007 Jun;23(6):555-8. 5. von Jagow B, Kohnen T. Corneal architecture of femtosecond laser and microkeratome flaps imaged by anterior segment optical coherence tomography. J Cataract Refract Surg . 2009 Jan;35(1):35-41. 6. Krueger RR, Dupps WJ Jr. Biomechanical effects of femtosecond and microkeratome-based flap creation: prospective contralateral examination of two patients. J Refract Surg. 2007 Oct;23(8):800-7. 7. Hamilton DR, Johnson RD, Lee N, Bourla 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 Dec;34(12):2049-56. 8. Buzzonetti L, Petrocelli G, Valente P, Tamburrelli C, Mosca L, Laborante A, Balestrazzi E. Comparison of corneal aberration changes after laser in situ keratomileusis performed with mechanical microkeratome and IntraLase femtosecond laser: 1-year follow-up. Cornea . 2008 Feb;27(2):174-9. 9. Shah R, Shah S, Sengupta S. Results of small incision lenticule extraction: All-in-one femtosecond laser refractive surgery. J Cataract Refract Surg . 2011;37(1):127-37. Editors’ note: SMILE and other ReLEx procedures are performed using the VisuMax femtosecond laser system, and are proprietary to Zeiss. Contact information Wang: +86-22-27305083, wangyan7143@vip.sina.com