Evolution of Femtosecond Laser: A new weapon in Refractive surgery Virendra Agrawal,MD,DNB; Anita Agrawal; Chitra Pandey,MS

ROS TIMES	ROS	RJO Home Page	Contact Us	About Us
Editor                                   Dr Sudhir Singh   Advisors Prof. P.K Mathur Dr  Pavan Shorey   Editorial Board Dr Anshoo Choudhary Dr Arun Kshetrapal Dr L S Jhala Dr Mayank Agrawal Dr Mukesh Sharma Dr Sandeep Arora Dr Sonu Goel Dr Subodh Saraf Dr Sukesh Tandon Dr Sunil Gupta Dr Suresh Kumar Pandey Dr Swati Tomar Dr Virendra Agrawal Evolution of Femtosecond Laser: A new weapon in Refractive surgery   Virendra Agrawal,MD,DNB; Anita Agrawal; Chitra Pandey,MS Corresponding Author  Dr Virendra Agrawal, Dr Virendra Laser, Phaco Surgery Centre Hospital - Tonk Phatak, Behind Mahindra Showroom, Gandhi Nagar, Jaipur drvirendra@yahoo.com Article Code RJO20110102 Introduction We are now entering a new era, where the field of refractive surgery is rapidly evolving by the femtosecond laser. The invention of the laser in 1960 stimulated renewed interest in optical physics and gave rise to a number of new research fields. One of them was the field of ultrafast optics, which had the beginning in the mid-1960s with the production of nanosecond (10-9 second) pulses by the first mode locked laser. Today, ultra short pulse generation remains the subject of active research. Rapid progress in this field has led to the creation of practical and useful lasers that can now produce pulses on the femtosecond (10 − 15 second)) time scale. [1]   Femtosecond is an ultrashort pulse of light is an electromagnetic pulse whose time duration is on the order of the femtosecond (10 − 15 second). Femtosecond lasers are solid-state Lasers which act on the principle of photodisruption. The application of many photons of laser energy at the same place and time leads to a nonlinear absorption of femtosecond laser energy. Due to the multiphoton effect, as well as the electron avalanche phenomenon, energy absorption by tissue eventually exceeds the threshold for optical breakdown. This process of photodisruption creates plasma. It also produces an acoustic shockwave, some thermal energy, and then a cavitation bubble, which expands at supersonic speed, slows down, and then implodes. A gas bubble subsequently forms that is composed of carbon dioxide, water, nitrogen, and other elements. [2]  The first commercially available femtosecond laser model, the IntraLase Femtosecond laser (Abbott Medical Optics Inc., Santa Ana, CA, USA), was introduced in 2001. Since then other femtosecond lasers,including the Femtec (Technolas Perfect Vision, Heidelberg, Germany), Femto LDV (Ziemer Ophthalmic Systems, Port, Switzerland), and the VisuMax (Carl Zeiss Meditec AG, Jena, Germany), have entered the market. [3] Blade versus Bladeless LASIK Femtosecond laser offers new possibilities in the field of refractive surgery especially when used as a microkeratome. Femtosecond laser is the first bladeless and most accurate modality for corneal flap creation available today. [28] Flap creation is the critical step of LASIK surgery. The mechanical microkeratome uses shear force traveling across the corneal stroma with an oscillating blade to create a flap (Blade LASIK). Femtosecond laser creates corneal lamellar flaps by producing a circular cleavage plane starting at one side and progressing across the cornea in a back and forth pattern (Bladeless or all-laser LASIK). It creates a flap edge of a programmable angle by using a circumferential pattern of progressively shallower pulses. A predefined arc along the edge is left uncut to create the hinge. The entire process takes place through a glass applanation plate that is fixed to the eye with a low-pressure suction ring. After that Excimer laser is applied to the newly exposed eye surface, where tissue is removed in a precise pattern to alter the cornea's shape.   All-in-one femtosecond laser surgery (ReLEx => FLEx and SMILE) ReLEx or refractive lens exchange, used to replace the natural lens of the eye with one that can reduce or eliminate the need for glasses. This procedure is possible with Visumax femtosecond laser machine. Within ReLEx, there are two procedures, FLEx, and SMILE. In FLEx (femtosecond lenticule extraction), the femtosecond laser is used to carve out a lenticule from within the cornea. The lenticule is then removed from within the cornea.This is done by lifting a flap and peeling off the lenticule. ReLEx can also be performed in a minimally invasive way. In this case, a small incision is made on the surface of the cornea, from where the lenticule is extracted from within the cornea. This means than no flap is created, nor is it lifted. This procedure is known as SMILE(small incision lenticule extraction). ReLEx, especially SMILE has several advantages for the patients over standard LASIK or Blade Free LASIK. These advantages include: • Less Dry Eyes • Better Corneal Strength • More stability of the result • No risk of flap displacement Advantages of Laser flaps over blade flaps The accuracy of the LASIK flap thickness is a key risk factor for flap complications and ectasia following LASIK. Predictability, reproducibility and precision of flap thickness, diameter and more defined angled edges, hinge location is much better when produced by femtosecond laser as compared to mechanical microkeratome.[23,24,25] The thinner the corneal flap the better, because this leaves a greater amount of corneal tissue under the flap for treatment. It maintains the corneal stability and avoids complications like ectasia. Femtosecond can create flaps as thin as 100 microns, as compared to microkeratomes that cut flaps ranging from 140-180 microns. Parameters like side cut angles, hinge size, location,, an oval flap in whatever shape is needed to better match the cornea. Femtosecond laser can also make an inverted side cut which makes flap stronger.These all eventually improve flap adherence and reduce the chance of surface cells of the cornea growing underneath and pushing up the flap (epithelial ingrowth) to create an irregular corneal surface with accompanying vision defects. Several studies have compared the visual outcomes of LASIK using the femtosecond laser versus mechanical microkeratome for creation of the flap. In which femtosecond laser proved to be produce better results. [26, 27] Smoother stromal bed is produced by femtosecond laser as compared to microkeratome. [22] Bladeless LASIK surgery can also be used in cases who have had previous corneal surgeries like radial keratotomy (RK), flap related complications, glaucoma,   Considering Complications: Blade Versus Bladeless. Uneven flap edges, buttonholing, heat or impact on surrounding tissue are the main disadvantages of blade LASIK, which are not found in case of bladefree-LASIK. There are also less chances of an eye infection or contamination during creation of the bladeless flap. This is because the tear film and other debris are not "dragged in" under the flap, as can occur with a blade flap maker. Other applications of femtosecond laser Once designed as a simple flap cutter for refractive surgery, the femtosecond laser is being used in new and exciting applications, including preparing cuts for intrastromal corneal ring segments, lamellar keratoplasty, and presbyopia correction etc. [4-6]   REFERENCES: 1.Wayne H and Knox: Ultrafast technology in telecommunications.IEEE Journal of Selected Topics in Quantum Electronics. 2000 Nov-Dec, volume: 6 Issue: 6:1273-1278. 2.JAY S. PEPOSE, MD, PHD, AND HOLGER LUBATSCHOWSKI, PHD:Comparing Femtosecond Lasers :An analysis of commercially available platforms for refractive surgery. OCTOBER 2008 I CATARACT & REFRACTIVE SURGERY TODAY: 45-51 3. Sugar A. Ultrafast (femtosecond) laser refractive surgery. Curr Opin Ophthalmol 2002;13(4):246–9. 4. Heisterkamp A, Ripken T, Mamom T, Drommer W, Welling H, Ertmer W, et al. Nonlinear side effects of fs-pulses inside corneal tissue during photodisruption. Appl Phys B 2002;74(4–5):419–25. 5. Noack J, Vogel A. Laser-induced plasma formation in water at nanosecond to femtosecond time scales: calculation of thresholds, absorption coefficients, and energy density. IEEE J Quantum Electron 1999;35(8):1156–67. 6. Vogel A, Noack J, Hüttman G, Paltauf G. Mechanisms of femtosecond laser nanosurgery of cells and tissues. Appl Phys B 2005;81(8):1015–47. 7. Dick HB, et al. Femtosecond laser in ophthalmology – A short overview of current applications. Med Laser Applic (2010), doi:10.1016/j.mla.2010.07.005 8. Bindewald A, Jorzik JJ, Loesch A, and Schutt F, Holz FG:Visualization of retinal pigment epithelial cells in vivo using digital highresolution confocal scanning laser ophthalmoscopy. Am J Ophthalmol . 2004 Mar; 137(3): 556-8. 9.Sarayba MA, Kurtz RM, Nquyen TT, Iqnacio T, Mansoori M, Sweet PM, CHUCK RS: Femtosecond laser-assisted intracornealkeratoprosthesis implantation : a laboratory model. Conea.2005 Nov;24 (8):1010-4. 10. Juhasz T, Kurtz RM, Sacks ZS, Mourau GA: High precision subsurface photodisruption in human sclera. J Biomed Opt. 2002 Jul;7 (3): 442-50. 11. Seitz B, Langenbucher A, Hofmann-Rummelt C, Schlötzer- Schrehardt U, Naumann GO: Non mechanical posterior lamellar keratoplasty using the femtosecond laser (femto-plak) for corneal endothelial decompansation. Am J Ophthalmol . 2003 Oct ;136(4):769-72. 12. Holzer MP, Rabsilber TM, Auffarth GU: Penetrating keratoplasty using femtosecond laser. A M j Ophthalmol. 2007 Mar;143(3):524-6. Epub 2006 Dec 18. 13. Blum M, kunert k, Nolte S, Riehemann S, Palme M, Peschel T, Dick M, Dick HB: Presbyopia treatment using a femtosecond laser. Ophthalmologe. 2006 Dec; 103(12):1014-9. 14. Krueger RR, Kuszak J, Lubatschowski H. Myers RI, Ripken T, Heisterkamp A: First safety study of femtosecond laser photodisruption in animal lenses: tissue morphology and cataractogenesis. J Cataract Refract Surg. 2005 Dec; 31 (12):2386 Links. 15. Ertan A, Bahadir M: Intrastromal ring insertion using a femtosecond laser to correct pellucid marginal corneal degeneration. J Cataract Refract Surg. 2006 Oct;32(10):1710 6. 16. Montės-Micó R, Rodriguez-Galietero A, Alió JL: Femtosecond laser versus mechanical keratome LASIK for myopia.Ophthalmology.2007 Jan; 114(1):62-8. Epub 2006 Oct Links. 17. Shabayek MH, Alió JL: Intrastromal corneal ring segment implantation by femtosecond laser for keratoconus correction. Ophthalmology. 2007 Mar 30;[Epub ahead of print]. 18. Soong HK, Malta JB, Mian SI and Juhasz T: Femtosecond laser-assisted lamellar keratoplasty. Arq Bras Oftalmol. 2008 Jul-Aug; 71(4):601-606. 19. Harissi-Dagher M and Azar DT: Femtosecond laser astigmatic keratotomy for postkeratoplasty astigmatism. Can J Ophthalmol. 2008 Jun; 43(3):367- 369. 20. Kim JH, Yum JH, Lee D and Oh SH: Novel technique of corneal biopsy by using a femtosecond laser in infectious ulcers. Cornea 2008 Apr; 27(3):363-365. 21. Yoo SH, Kymionis GD, O'Brien TP, Ide T, Culbertson W and Alfonso EC: Femtosecond-assisted diagnostic corneal biopsy (FAB) in keratitis. Graefes Arch Clin Exp Ophthalmol. 2008 May; 246(5):759-762. 22. Sarayba MA, Ignacio TS, Binder PS, Tran DB. Comparative study of stromal bed quality by using mechanical, IntraLase femtosecond laser 15- and 30-kHz microkeratomes. Cornea 2007;26:446-51. 23. Kezirian GM, Stonecipher KG. Comparison of the IntraLase femtosecond laser and mechanical keratomes for laser in situkeratomileusis. J Cataract Refract Surg 2004;30:804-11 24. Binder PS. Flap dimensions created with the IntraLase FS laser. J Cataract Refract Surg 2004;30:26-32 25. Kim JH, Lee D, Rhee KI. Flap thickness reproducibility in laser in situ keratomileusis with a femtosecond laser: Optical coherence tomography measurement. J Cataract Refract Surg 2008;34:132-6 26. Durrie DS, Kezirian GM. Femtosecond laser versus mechanical keratome flaps in wavefront-guided laser in situkeratomileusis: Prospective contralateral eye study. J Cataract Refract Surg 2005;31:120-6 27. Tanna M, Schallhorn SC, Hettinger KA. Femtosecond laser versus mechanical microkeratome: A retrospective comparison of visual outcomes at 3 months. J Refract Surg 2009;25: S668-71 28. Kezirian GM and Stonecipher KG: Comparison of the IntraLase femtosecond laser and mechanical keratomes for laser in situ keratomileusis. J Cataract Refract Surg.2004 Apr; 30(4):804-811.  Disclaimer Rajasthan Journal Of Ophthalmology An Official Publication Of The Rajasthan Ophthalmological Society
Chief Web Editor Dr Sudhir Singh All Rights Are Reserved To Rajasthan Ophthalmological Society