Femtosecond Laser

the flap, or moved in a “windshield-wiper” motion across the cornea [4]. Surgeons who have started on 5, 10, or 15 Hz-femtosecond technology have chosen this technique because of its easy adaptability under the circumstances of rather imperfect photo disruption at the beginning of the aera of femtosecond laser corneal surgery. One dis- advantage, however, is that the steel instrument intrudes into a preformed corneal space, and there is a potential for via falsa penetration (Figure 12) of the tissue with the steel instrument in the case of imperfect photo dis- ruption of the corneal layers. Due to the varying initial interactions between the corneal tissue and the CO bub- bles formed by the femtosecond laser, effects of vertical or horizontal breakthrough may occur. The forming of an opaque bubble layer of softened and weakened tissue enables the perforation by the rectangular design of the Seibel-IntraLASIK Flap Lifter. To avoid this, the Femto- flapLIFTER has been given a curved physiologically better design (Figure 1). In some cases, the surgeon may not be able to exit the side cut at the opposite side of the hinge. To solve this problem the surgeon has to find variations from the intended plan. He can now widen the gap between corneal stroma and flap from hinge to pe- riphery by moving the instrument in a “multilane” fash- ion several times across the cornea to widen the dissec- tion space. Generally, in the hinge opening technique, the cooperation of the patient is needed [4] to counteract the said manipulations of the instruments by activation of the patient’s eye muscles (Figure 12). Some patients ex- perience frightening sensations here because they expect a gentle “bladeless” LASIK. In a complicated case, the intrusion of the instrument may also increase the chance of tissue damage and potential implantation of epithelial cells or detritus into the interface due to prolonged ma- nipulation. Thus, in otherwise uneventful treatments, microstriae are sometimes visible in the first postopera- tive week due to the mechanical stress on the flap’s inner

The femtosecond laser induced micro- and nanostructures for the application to the three- dimensional optical data storage are investigated. We have observed the increase of refractive index due to local densification and atomic defect generation, and demonstrated the real time observation of photothermal effect after the femtosecond laser irradiation inside a glass by the transient lens (TrL) method. The TrL signal showed a damped oscillation with about an 800 ps period. The essen- tial feature of the oscillation can be reproduced by the pressure wave creation and propagation to the outward direction from the irradiated region. The simulation based on elastodynamics has shown that a large thermoelastic stress is relaxed by the generation of the pressure wave. In the case of soda-lime glass, the velocity of the pressure wave is almost same as the longitudinal sound velocity at room temperature (5.8 m/ns). We have also observed the localized photo-reduction of Sm 3+ to Sm 2+ inside a transparent and colorless Sm 3+ -doped borate glass. Photoluminescence

Purpose: To develop a new method of femtosecond laser-assisted refractive autokeratoplasty (FRAK) in advanced keratoconus and to evaluate preliminarily early clinical results. Methods: A total of 17 patients with stable advanced keratoconus and a mean age of 33 ± 8.4 years were in- cluded in the study. FRAK was performed in all cases with the IntraLase 60 kHz (Abbott Medical Optics Inc.). A 2-step resection of corneal stroma was performed using the femtosecond laser, with the generation of a circular corneal flap with wedge-shaped profile. After flap removal, the corneal wound was sutured. Results: The surgical procedure and early postoperative period were un- eventful in all cases. Mean uncorrected distance visual acuity (UDVA) improved significantly from 0.07 ± 0.03 preoperatively to 0.26 ± 0.13 at 3 months after surgery. Improvement in corrected distance visual acuity (CDVA) was observed in 94.1% of cases, with 76.5% of eyes showing an im- provement of more than 3 lines. Between 3 and 6 months after surgery, an additional improve- ment was observed in UDVA and CDVA. Corneal cylinder decreased significantly from 9.1 ± 3.8 D preoperatively to 4.4 ± 2.75 D at 6 months postoperatively. Conclusions: FRAK may be an alterna- tive treatment in stable advanced keratoconus, allowing a significant visual improvement and corneal regularization while saving the patient's own corneal tissue. The non-penetrating nature of the surgical technique helps to minimize the risks associated to this type of surgery. Further research is needed to determine the functional long-term outcomes.

In most cases, surgeons can manually achieve a perfect rhexis, but the patients may inadvertently move, rendering the rhexis imperfect. Younger patients are more anxious about premium lens implantation and are more likely to move during surgery. This can lead to an imperfect capsulorhexis, caus- ing lens tilt, which inevitably leads to an increase in higher order aberrations, leaving the patients with a postoperative visual acuity that is not as good as it could be. Therefore, even high-volume cataract surgeons need a reliable technol- ogy achieving attainable, consistent results, especially when advanced technology intraocular lenses (IOLs; multifocal, accommodative, aspheric, toric, toric-multifocal, etc) are used. The new femtosecond laser technology may offer these advantages.

Purpose: To evaluate the collective user experience with an image-guided femtosecond laser (FSL) for cataract surgery in a high-volume, multi-surgeon, ambulatory surgical center. Subjects and methods: A detailed online survey was distributed to all surgeons in a single ambulatory surgical center who had performed cataract surgery using a FSL since its acquisi- tion in December 2012. Information collected included the number of cases performed, typical surgical techniques and parameters, satisfaction with individual features of the laser (rated on a scale from 1=completely unsatisfied to 10=extremely satisfied) and commentary on ease of use and suggested improvements.

At this institution, laser-assisted surgery is taught in con- junction with routine phacoemulsification at both PGY3 and PGY4 levels, with greater emphasis on FLACS during later stages of training. This study characterizes the comparative efficiencies of senior ophthalmology residents when perform- ing FLACS, which was generally found to be less efficient than traditional surgery in the training program setting. Sig- nificantly longer times were demonstrated in association with FLACS for total OR time, microscope operating time, and corneal incision completion time. Interestingly, the difference of mean total room time only slightly exceeded the difference of mean operative time, suggesting that laser pretreatment did not substantially increase average room time. Extended time for femtosecond laser use could have been anticipated due to the 2-step nature of the procedure, but this study indicates that extension of the manual portion of the surgical procedure was the primary factor contributing to higher room times for FLACS cases. The source(s) of higher mean operative time in the FLACS group was not identified by our analysis of individual core steps, and the cause remains unclear. There are other procedural components not studied that might have contributed to decreased efficiency such as capsular staining dye use, viscoelastic injection, laser-generated gas bubble removal, hydrodissection, or confirmation of watertight wound closure. Additional non-technical factors that could potentially prolong FLACS OR times or proce- dure times include supervising attending instruction, patient restlessness, room design, operating table design, instru- ment access, duplication of time-out procedures, or lesser familiarity with FLACS by scrub technicians.

The introduction of femtosecond lasers to cataract surgery has been the major disruptive technology introduced into ophthalmic surgery in the last decade. Femto- second laser cataract surgery (FLACS) integrates high-resolution anterior segment imaging with a femtosecond laser allowing key steps of the procedure to be performed with computer-guided laser accuracy, precision, and reproducibility. There are cur- rently five femtosecond laser platforms available and approved for use during cataract surgery. The LenSx platform (Alcon Laboratories, Inc., Fort Worth, TX, USA) was the first laser to obtain both the US (Food and Drug Administration) and European (Conformité Européene, CE Mark) approval and was commercially released in 2011. Since then, more than 950 laser platforms have been installed in 67 countries with 3,500 surgeons trained and over 800,000 procedures completed using the LenSx. The scientific literature has provided over 250 peer-reviewed articles, ranging from randomized controlled trials to cohort studies, case reports, and editorials. This review examines the published evidence relating to the LenSx platform and discusses surgical techniques, indications, and clinical results relating to capsulotomy, phacoemulsi- fication and lens fragmentation, corneal wound creation, and visual results. Safety issues relating to capsular integrity and corneal endothelial and macular changes are also discussed.

nearly flawless surgical skills and is associated with a high risk of irregular astigmatisms, which are difficult to rectify and are associated with unpredictable complica- tions; thus, the traditional AK technique is often per- formed to correct only moderate-to-high astigmatisms. With the introduction of FSAK, the precision of this procedure, including arc length, depth, and location, has been greatly enhanced relative to that of manual inci- sions, making it suitable for low-to-moderate corneal astigmatisms. FSAK creates single or paired arcuate cor- neal incisions at the steeper axis of astigmatism, through femtosecond laser guidance [16, 17]. The LRIs, also known as peripheral corneal relaxing incisions (PCRIs), are made more peripherally in the cornea. These inci- sions are easy to create and are associated with a lower risk of irregular astigmatism and unpredictable compli- cations, making them suitable for low-to-moderate cor- neal astigmatism [18]. In clinical studies of FLACS combined with corneal refractive surgery, FSAK and femtosecond laser LRI (FS-LRI) are often considered as one entity. They are both defined as arcuate corneal in- cisions of 8.5–9.0-mm arc diameter at the steep axis of astigmatism, made through femtosecond laser assistance. FLACS can also be combined with the femtosecond laser nonpenetrating intrastromal astigmatic keratotomy (ISAK) to correct low-to-moderate astigmatism; in this technique, the incisions are made intrastromally and re- tain 60 – 100 μ m of corneal tissue anteriorly and poster- iorly [19 – 21].

The recently introduced solid-state femtosecond laser cre- ates corneal flaps for laser in situ keratomileusis (LASIK). It uses a 1053 nm infrared wavelength neodymium:glass that deliver microspots to photodisrupt tissue within the corneal stroma, creating cavitation bubbles that expand and coalesce, forming a resection plane. 1–3 The femtosec- ond laser seems to have advantages over mechanical micro- keratomes including improved predictability of the flap thickness and diameter, better flap uniformity, better pre- dictability of hinge position and size, astigmatic neutrality, and reduced incidence of epithelial defects, buttonholes, and cap perforation. 4–5 However, other complications, such as delayed-onset photophobia, corneal folds, and in- terface inflammation, have been reported. 4,6

The absorption of ultraintense, femtosecond laser pulses by a solid unleashes relativistic electrons, thereby creating a regime of relativistic optics. This has enabled exciting applications of relativistic particle beams and coherent X-ray radiation, and fundamental leaps in high energy density science and laboratory astrophysics. Obviously, central to these possibilities lies the basic problem of understanding and if possible, manipulating laser absorption. Surprisingly, the absorption of intense light largely remains an open question, despite the extensive variations in target and laser pulse structures. Moreover, there are only few experimental measurements of laser absorption carried out under very limited parameter ranges. Here we present an extensive investigation of absorption of intense 30 femtosecond laser pulses by solid metal targets. The study, performed under varying laser intensity and contrast ratio over four orders of magnitude, reveals a significant and non-intuitive dependence on these parameters. For contrast ratio of 10 −9 and intensity of 2 × 10 19 W cm −2 , three observations

In order to discuss the feasibility of compact neutron sources for scientific, medical and industrial appli- cations, the yield of laser-produced neutrons is scaled by the laser energy. The laser energy scaling law of the neutron yield is derived from the laser intensity scaling law for the energy and the number of laser produced ions. High-energy ions are generated by Coulomb explosion of clusters through intense femtosecond laser-cluster inter- actions. The reactions of D(D,n)He generating high yield even by relatively low deuterium energy and Li(p,n)Be generating relatively low energy neutrons are discussed. The neutron yield of D(D,n)He determines the potential for using compact neutron sources with the aid of modern laser technology. In addition, p(Li,n)Be shows much higher yield than Li(p,n)Be with the assumption of Coulomb explosion of a cluster with a diameter of 500 nm.

Femtosecond laser treatment represents a novel and attractive method for in vivo gene delivery because the lasers are convenient to operate, relatively non-invasive, and have been shown to significantly enhance gene trans- fection efficiency without detectable tissue damage in mice [14,15]. They have been applied toward in vitro genetic modification of cells (for a review, see [16]) and have recently been found to improve intradermal and intramuscular delivery of DNA in mice [14,15]. Therefore, in the current study, we employed femtosecond laser treatment in an effort to improve the transfection effi- ciency of DNA encoding luciferase that was administered intradermally as well as intratumorally in mice, with the hope of finding an innovative technology that may be used both for DNA vaccination as well as for plasmid DNA gene therapy in the clinical setting.

Femtosecond laser is a perfect laser source for materials processing when high accuracy and small structure size are required. Due to the ultra short interaction time and the high peak power, the process is generally characterized by the absence of heat diffusion and, consequently molten layers. Various induced structures have been observed inside glasses after the femtosecond laser irradiation. Here, we report the refractive index change, space-selective valence state manipulation of active ions and precipitation control of nanoparticles by a femtosecond laser in glasses. We have recently observed the three-dimensional nanostructuring such as a nano-grating and a nano-void inside a glass material by the single laser beam irradiation. The self-organized sub-wavelength periodic nanostructures are created by via a pattern of interference between the incident light field and the electric field of the bulk electron plasma wave. The mechanisms of the observed phenomena were also discussed. Furthermore, we observed the space-selective structural-phase transformation from diamond to amorphous structure which has electrically conductive property.

The concern with the use of femtosecond laser to re- move the chestnut was the spreading of infections. The mature chestnut contains clusters of sharp and yellow-brown thorns that might harbor filamentous fungi leading to fungal keratitis [9]. In this case, the fun- gal infection was excluded. Because no sign of infections was noted, the cornea and the anterior chamber seemed to be quiet after injury, and postoperatively, the corneal

The mirror-finished surface of pure copper (99.99%) was heated to 100°C on a hot plate and then adhered to PET, which had a thickness of 1 mm and was softened by the heat from Cu. The oxide layer on Cu was removed by hydrochloric acid just before the adhesion. Table 1 shows the thermal properties of Cu and PET. Femtosecond laser pulses (Spectra-Physics Spitfire) with a wavelength of 800 nm, a pulse width of 130 fs and a pulse energy of 10 µJ were focused using a plano-convex lens with a focal length of 70 mm through PET onto the Cu surface, as shown in Fig. 1. We defocused 600 µm from the focal point, resulting in the diameter of the ablated region of around 34 µm. We here de fi ne the distance between pulses in the x-direction as the pulse-to-pulse distance d x and those in the y-direction as the

The IntraLase femtosecond laser was used to create the flap. The laser software creates a circular cleavage plane starting at one side of the cornea and progressing across the cornea using a raster pattern. After the horizontal cleavage plane is created, the pattern changes to a vertical one, continuing through Bowman’s layer and the epithelium. It then creates a flap edge with a programmable angle using a circumferential pattern of shallower pulses. An arc along the edge is left uncut to create the hinge. The software controls the planned flap diameter and thickness, angle of the side cut, hinge size and location, and all energy settings to create the flap.

environment. With this femtosecond device, the centra- tion of the flap can be repositioned within a 10.0 mm di- ameter area, even after the suction ring has been applied. Via a computer network, the ablation profile is fed to the femtosecond laser, where it can be superim- posed on the cornea to adjust the flap profile to fit the ablation. By shifting the placement grid, the surgeon can customize flap placement to best fit the planned ab- lation. The femtosecond laser releases infrared laser pulses in a raster pattern onto the cornea, resulting in the formation of small cavitation bubbles within the tis- sue. The creation of thousands of cavitation bubbles in a lamellar pattern leads to the creation of a cleavage plane within the cornea. Subsequently, laser pulses are fired in a peripheral circular pattern onto the corneal stroma to create a vertical side cut and a hinge. This la- ser can make large-diameter corneal applanation zones, up to 13.0 mm, allowing comfortable margins when performing hyperopic LASIK. It automatically cuts a square tunnel through the flap's hinge that allows the cavitation gas to escape to minimize the develop- ment of an OBL. In addition, the beam target, size, and spacing are optimized to minimize the OBL, allow- ing the surgeon to perform an excimer laser treatment immediately after flap creation.

Propagation of filamented femtosecond laser pulses in fused silica is studied us- ing microscopic techniques of time-resolved femtosecond optical polarigraphy and transient absorption. Basing on the value of induced absorbance measured at the trailing edge of propagating pulse, it is concluded that the filament is refilled by energy flux from a reservoir. Light energy and plasma density in the filament core, along with the corresponding changes in refraction index, are estimated. Reshaping of the laser pulse caused by expulsion of light from the plasma- occupied area is directly observed. Transformation of axially symmetric shape of the pulse into asymmetric Z-like one is also found.

Kezirian and Stonecipher have reported fewer complica- tions, better flap thickness predictability, and less surgi- cally induced astigmatism in eyes treated with FS-LASIK compared to the Hansatome (Bausch & Lomb, Rochester, New York) and Carriazo-Barraquer (CB) microkeratome (Moria, Antony, France) [8]. Pajic et al. found the femto- second laser (Technolas) to be superior to the mechanical microkeratome (Amadeus II) in terms of flap thickness predictability and the speed of visual acuity recovery in a prospective, randomized, paired eye study [9]. Flap diameter, thickness accuracy, [9–15] and flap thickness reproducibility [13] have been consistently shown to be superior in femtosecond created flaps compared to micro- keratome assisted flap creation. Recently, Zhang et al. [16] investigated the thickness and the morphology of the WaveLight FS200 (Alcon Laboratories Inc., Fort Worth, Texas, USA) femtosecond laser microkeratome compared with microkeratome flaps, using anterior segment optical coherence tomography (AS-OCT). Femtosecond created flaps were found to deliver more accurate, reproducible flaps with uniform thickness compared to those created by the Moria microkeratome (Moria SA, Antony, France). Electron microscopy [17] has shown that the quality of the stromal bed surface in flaps created with the Moria or the 15 kHz IntraLase were com- parable in quality and surface characteristics. In addition, the 30 kHz IntraLase provide better stromal bed characteristics compared to Moria and the 15 kHz IntraLase [17].

with high precision. Femtosecond laser-assisted AK (FSAK) is well proven to be effective and safe in redu- cing corneal astigmatism in highly astigmatic eyes after penetrating keratoplasty (PKP) [2, 3]. Patients who underwent PKP or deep anterior lamellar keratoplasty (DALK) might have substantial anisometropia; the pri- mary goal of FSAK is the reduction of astigmatism after PKP to a level that allows the patient to wear contact lens or spectacles. This concept is important since the sequel of AK is somewhat unpredictable [4] and may re- quire other visual aids. FSAK also can be performed to treat corneas that are too thin for refractive surgery or unsuitable for enhancement because of insufficient cor- neal tissue or severe dry eye [5].