1. Femtosecond lasers are lasers that emit light pulses, the duration of them are in the femtosecond range. The spreading speed of these lasers travels within one femtosecond ( 1fs= 10^15 s ). Femtosecond lasers have been used successfully in ophthalmic surgery since 2001. The technology has been applied widely most common know today in LASIK (Laser in Situ Keratomileusis) refractive surgery. In Femtosecond lasers technique the femtolasik laser replaces a mechanical device, microkeratome, to create a precise corneal flap preparing the eye for the secondary laser ablation in order to change the patient’s refractive error. There are several benefits, Femtosecond lasers have been noted to be more precise than microkeratomes, with fewer likely collateral tissue effects.

2. The femtosecond laser was first used clinically in cataract surgery by professor Zoltan Nagy in Budapest in 2001. The role of femtosecond lasers cataract surgery is to assist or replace several aspects of the manual small incision cataract surgery. These include the creation of the initial surgical incision in the cornea, the creation of the capsulotomy and the phacofragmentation, the initial fragmenting of the lens. The femtosecond laser may also produce incisions within the peripheral cornea to aid the correction of pre-existing astigmatism. Femtosecond laser energy is absorbed by the tissue, resulting in plasma formation. This plasma of free electrons and ionized molecules rapidly expands, creating cavitation bubbles. The force of the cavitation bubble creation separates the tissue. The process of converting laser energy into mechanical energy is known as photodisruption. Currently, 4 femtosecond laser technology platforms are commercially available for cataract surgery: Catalys (Optimedica), Lensx (Alcon Laboratories, Inc.), Lensar (Lensar, Inc.), Victus (Technolas).

3. Preoperative Planning for FLACS Surgery: First, detailed planning of each stage of the operation is required. This involves: assessing the anatomy of the patient's eye taking into account pupil diameter anterior chamber depth, and thickness of the lens and cornea. Size, shape, and centration of the capsulotomy are then calculated, with the choice of IOL in mind. The type of lens fragmentation or liquefaction is chosen and customised by the surgeon, as this will have a bearing on the amount of phaco time and power, which is required subsequently. Parameters for the location, structure, and depth of the clear corneal incisions (CCIs) are inputted. If astigmatic relieving incisions are to be performed, their depth, length, and axis are currently determined by traditional nomograms.

4. PROCEDURE FOR FLACS: Docking Proper docking requires the patient to be flat on the table with minimal neck support. The head must be secured with a slight tilt so the operated eye is in a higher plane to clear the nose and achieve proper applanation. The patient must be able to remain still for the several minutes required for accurate imaging followed by application of laser energy. There are also different patient-interface systems, which can be divided into contact (applanating) and noncontact (nonapplanating).

5. Contact systems tend to have a smaller diameter and may fit a smaller orbit better. They also provide a separate reference plane for anterior cuts such as a flap. Noncontact devices, in addition to less increase in intraocular pressure (IOP), cause less subconjunctival hemorrhage and offer a wider field of view. Imaging All the femtosecond laser platforms use either spectral-domain optical coherence tomography (OCT) or ray-tracing reconstruction (3-dimensional confocal structural illumination [3-D CSI]) to image and map the treatment plan. The cornea must be centered within the applanated area to adequately center the treatment. If not, capsulorhexis could be decentered, potentially resulting in decentration of the intraocular lens (IOL). It is crucial in astigmatic patients in whom decentration could result in arcuate incisions within the visual axis or a wound posterior to the limbus. During the acquisition phase, the patient must remain still for up to a few minutes while the image is being captured. The capsulorhexis is then centered within the pupillary border.

6. The Treatment Stage The diameter of the capsulorhexis is typically defined in settings prior to the procedure (approximately 5.0 mm in most cases) but can be modified according to pupillary dilation and IOL selection. The surgeon chooses a lens fragmentation pattern based on the density of the nucleus and surgeon preference. They may choose the number of segments as well as the degree of lens softening depending on the lens grade. Commonly used patterns include 4, 6, or 8 segments with or without the use of lens softening. A surgeon-defined safety zone from the posterior capsule (typically 500 to 800 mm) is automatically applied by the imaging platform and visualized on the OCT guidance for approval by the surgeon before the laser is applied. The capsulorhexis is performed first and takes 1.5 to 18.0 seconds, followed by lens fragmentation and ultimately corneal wound creation.

7. Each laser incision is constructed in the posteroanterior plane, a principle that elegantly employs the posterior microcavitation bubbles to scatter the laser beam and reduce the amount of energy reaching the retina. By keeping the bubbles posterior to the laser target, the focus of the laser beam is maintained and this avoids scatter before the target tissue. Once the laser treatment has been completed, the suction is released, the patient interface is removed, and the patient is slowly undocked from the laser. Then the surgeon can proceed with phacoemulsification immediately or wait up to 2 to 3 hours between the 2 stages of the procedure. Due to progressive pupillary miosis, it is recommended that phacoemulsification occur within 30 to 40 minutes of the femtosecond laser procedure.

8. Femtosecond laser currently has four applications in cataract surgery: astigmatic limbal relaxing incisions (LRIs), corneal wound construction, anterior capsulotomy (or laser-incised capsulorhexis), and lens fragmentation. http://www.youtube.com/watch?v=r5kwgxdI-SE

9. Femtosecond laser in ophthalmology: We stand at the threshold of a revolution, which is guided by the femtosecond laser. With its expanding repertoire of uses, this laser will soon be used in almost every aspect of ophthalmic science. From its beginning in LASIK, it has gone on to Intra-Corneal Ring Segments and keratoplasties. The femtosecond laser is now going to treat cataracts. From capsulotomy to nuclear softening and chopping as well as creation of side ports and corneal incisions, everything is now possible with the femtosecond laser. It uses an infrared beam of light to precisely separate tissue through a process called photodisruption by generating pulses as short as one-quadrillionth of a second. It has wavelength of 1053 nm and is based on the technology whereby focused laser pulses divide material at the molecular level without transfer of heat or impact to the surrounding tissue.

10. Its most popular use lies in the creation of a corneal flap in a lasik procedure. The laser beam is focused on a pre-programmed depth and position within the cornea with each pulse forming a microscopic bubble. As the laser moves painlessly back and forth, the bubbles connect to form a flap with no trauma, the entire process taking around 10-20 seconds. The surgeon then lifts the flap to allow treatment by excimer laser. The laser also creates a distinctive beveled edge flap which allows precise repositioning and alignment after Lasik is completed. The precision of the femtosecond laser helps to create flaps of exact size, shape and depth and reduces the risk of blade-related complications such as free caps, incomplete or decentered flaps. Also, visual acuity is better and post-op dry eye symptoms are reduced. It also creates fewer high and low-order aberrations which may cause glare and haloes at night.

11. The femtosecond laser has also revolutionized other forms of corneal surgery such as corneal transplantation and Intrastromal ring implantation. It enables surgeons to create straight, angled and arcuate incisions which allow faster healing and improved visual recovery in penetrating keratoplasty. The mushroom shaped incision preserves more host endothelium. The “zigzag” incision approach provides a smooth transition between host and donor tissue and allows for a hermetic wound seal, Intralase Enabled Keratoplasty establishes secure grafts requiring less suture tension and reduce incidence of astigmatism leading to a faster and better visual recovery. The femtosecond laser is also used for insertion of intra-corneal ring segments (ICRS) in the treatment of keratoconus and corneal ectasia. It creates channels at a pre-determined depth with a high degree of accuracy. The entry wound and channel creation takes 8-10 seconds after which the entry wound is opened with a Sinskey hook and the ring segment is carefully pushed forward in the channel till the edge lies within 1 mm from the entry wound.

12. The introduction of newer generations of femtosecond lasers which have a higher frequency, offer greater precision, control and safety and reduce the time spend during the procedure. Additional features include variation in the flap shape and diameters to allow for elliptical flaps for better results in hyperopic patients. Another feature is the change in angulation of the flap edge to achieve a better flap apposition and more secure flap healing with greater stability. A study of the LenSx laser at Semmelweis University in Budapest, Hungary, found that all anterior capsulotomies created with the laser achieved accurate centration and intended diameter, with no radial tears or adverse events. Only 10% of manually created capsulorhexes achieved a similar diameter accuracy of ± 0.25 mm. The results were reported at the 2009 American Academy of Ophthalmology meeting.

13. Clinical Results: Femtosecond laser-assisted corneal incision Masket et al., conducted a cadaver eye study in which they showed decreased leakage, added stability, and reproducibility at various IOPs after FSL-guided corneal incision. Additionally, Palanker et al., observed they could create an incision using the FSL that formed a one-way, self-sealing, and water-tight valve under normal IOP. No authors have published data on the rate of postoperative endophthalmitis with the advent of FSL-guided incision in cataract surgery, and there are no published comparative studies between standard keratome and FSL-guided incisions. Femtosecond laser-assisted capsulorhexis Nagy et al., performed anterior capsulotomies in 54 eyes, comparing the LenSx laser to manual capsulorhexis 1 week after cataract surgery. In the FSL group, the authors observed a higher degree of circularity, fewer patients with incomplete capsulorhexis-IOL overlap (11% of laser patients compared to 28% of manual capsulorhexis patients), and better IOL centration.

14. FSL-guided capsulotomy diameter did not show correlation to pupil diameter, eye size, or curvature of the cornea, assuming the pupil was appropriately dilated. However, manual capsulotomy size was directly correlated with these variables. This suggests that manual capsulotomy is prone to deceptive influence from the pupil size, eye size, and curvature of the cornea, while laser capsulotomy avoids this inappropriate influence. Using the OptiMedica FSL platform, two studies similarly demonstrated a statistical advantage for the FSL-assisted capsulotomy in terms of precision, accuracy, and reproducibility in human eyes.

15. Femtosecond laser-assisted phacofragmentation Preliminary work has shown that FSL systems reduce ultrasound energy necessary for all grades of cataract. Nagy et al., showed that the FSL reduced phacoemulsification power by 43% and operative time by 51% in a porcine eye study. Two studies have compared human eyes receiving FSL-assisted capsulorhexis and phacofragmentation to fellow eyes receiving traditional cataract surgery. Both show easier phacoemulsification in the FSL group. In one of these studies, Palanker et al. observed a decrease in the perceived hardness of nuclear sclerotic cataract after the laser-assisted procedure, estimated by the surgeon to decrease from grade four to grade two. A 39% average reduction in dispersed energy for phacoemulsification was also observed in the FSL group. Furthermore, they showed that with grade three or higher cataracts, FSL-assisted lens fragmentation also reduced the amount of energy, suggesting fewer complications for these more difficult cataracts.

16. The introduction of femtosecond lasers to cataract surgery has generated much interest among ophthalmologists around the world. Laser cataract surgery integrates high-resolution anterior segment imaging systems with a femtosecond laser, allowing key steps of the procedure, including the primary and side-port corneal incisions, the anterior capsulotomy and fragmentation of the lens nucleus, to be performed with computer-guided laser precision. There is emerging evidence of reduced phacoemulsification time, better wound architecture and a more stable refractive result with femtosecond cataract surgery. Also, Femtosecond laser surgery is a great experience not only for the surgeon, but also for the patient, because it offers very good results, is a really fast procedure and is almost painless for the patient.

17. Limitations: Current studies support the safety and efficacy of FLACS, although small patient populations and short-term follow-up limit the ability to assess such safety factors as the frequency of discontinuous FSL- assisted capsulorhexis and associated anterior capsular tears. There are a lot of unanswered questions at this point. For FSL-assisted corneal incision,, it is important to research the difference in postoperative endophthalmitis rates after laser-assisted corneal incision. Although this research will be a difficult, because it requires very large patient populations, this is a key question because postoperative endophthalmitis is the terminal outcome measure that will ultimately justify FSL use in corneal incisions.

18. There are no available studies using large enough patient populations to accurately assess complication rates. The longest study is limited to 1 year of follow-up. This study focused on centration parameters only. The limitations of FLACS are not well-established at this time. Based on relative contraindications to FSL refractive surgery, we hypothesize similar contraindications may apply to FLACS. Logically patients who have deep set orbits or those with tremors or dementia may do poorly with the initial docking of the lens that requires patient cooperation. Other exclusions may be anterior basement membrane dystrophy, corneal opacities (e.g. arcus senilis, corneal dystrophies, and trauma- or contact lens-induced scars), ocular surface disease, pannus with encroaching blood vessels, or recurrent epithelial erosion syndrome.

19. The level of increase in IOP induced by the docking device has not been adequately quantified. This may be an important contraindication for patients with glaucoma, optic neuropathies, or borderline endothelial pathology. Lastly, diabetics may have undiagnosed epithelial disease making them prone to epithelial defects. Because FLACS relies on anterior segment imaging for laser pattern mapping, any patients with poor dilation would be poor candidates. Such patients would be those with posterior synechiae, intraoperative floppy iris syndrome suspects, or those on chronic miotic medications. High-quality images for mapping of the posterior lens are critical. More studies are also needed to assess if dense posterior subcapsular cataracts, those with vacuoles, anterior subcapsular cataracts, and other types or combinations of cataracts will perform differently with FSL-assisted phacofragmentation.

20. Additionally, having a stable, stationary lens is needed for precise laser mapping and execution. Patients with phacodonesis and zonular dialysis, or those with risk factors such as pseudoexfoliation types or combinations of cataracts will perform differently with FSL-assisted phacofragmentation. A stable, stationary lens is needed for precise laser mapping and execution. Patients with phacodonesis and zonular dialysis, or those with risk factors such as pseudoexfoliation syndrome or trauma, may not be ideal candidates. The final issue for FLACS is cost. There is no doubt that this technology has added costs, although we have seen that patients are willing to pay out of pocket for new technology if they view it as being safer or offering better results. Similarly, patients will likely be willing to pay extra if they perceive that they will achieve better results with laser- assisted cataract surgery. Cost-benefit analysis has not yet been addressed.