Femtosecond

Update on Femtosecond Technology

Use this information to discuss the latest developments and uses of femtosecond lasers with your patients.

Marc R. Bloomenstein, O.D., F.A.A.O.

If you don't stay up-to-date on the latest technology and provide patient education on this technology, you risk losing patients. It's that simple. This is particularly the case with surgery: Provide patient education on the latest surgical techniques and invite questions, and the patient will likely return to you. Fail to do so, and you have an excellent chance of losing the patient to the surgeon.

Keeping this all in mind, here, I discuss the latest Femtosecond technology, so you can educate your patients.

In brief: Femtosecond lasers emit optical pulses of extremely short duration in the domain of femto-seconds (one-quadrillionth of a second). These ultrashort pulses do not transfer heat or shock to the material being cut and can make surgical incisions with extreme precision.

Studies have concluded that femtosecond lasers create thin, more precise flaps than mechanical microkeratomes. Aside from the safety aspect, decreased dryness, quicker healing times, faster visual recovery and better acuities have been reported with the use of the femtosecond laser for the flaps.

As a result, the femtosecond laser is now being applied to all corneal surgeries and can turn a once surgeon-dependent procedure into a more predictable and standard process.

Lens applications

Currently, femtosecond technology is an option for cataracts and has shown promising results in a noninvasive way to help ward off cataracts. The in-vivo bleaching of age-induced yellowing on the human crystalline lens may prove to be just that method. Researchers in Denmark used an 800nm femtosecond-pulsed laser to bleach human donor lenses. Following treatment, the age-induced yellow discoloration was markedly reduced, and the transmission of light was increased. Femtosecond bleaching corresponded to an optical rejuvenation of three-to-seven years, according to the study's researchers.¹

The four systems approved for cataract indications, including anterior capsulotomy and phacofragmentation are:

► LenSx. The LenSx Laser system, from Alcon, uses a proprietary optical coherence tomography (OCT) system to provide real-time images of the anterior segment. Although the order of the procedure can be customized, most surgeons work from the inside out; thus, the cataract procedure is performed in reverse compared with standard surgery. First, the cataract is fragmented. Then, the anterior capsulotomy is created. From there, the corneal incisions are performed. Once the incisions are complete, the surgeon uses irrigation/aspiration to remove the fragmented cataract, performs cortical clean-up and implants the intraocular lens (IOL).

► LensAR. The LensAR Laser System integrates proprietary automated biometry, ocular imaging and measurement technology. It measures ocular anatomy and guides the laser based on the images obtained and automates most of the manual incisions and prefragmenting of the lens. Further, it significantly reduces cumulative dissipated energy (CDE) for all grades of cataracts and should contribute to more reliable and predictable surgical outcomes, the company says. Finally, the laser uses a no-touch patient interface for safety, comfort and ease of use.

► Catalys Precision Laser System. This system, from Opti-Medica, features a Liquid Optic Interface designed to provide a stable, yet comfortable patient dock and a clear optical path for the OCT and laser. In addition, Catalys is equipped with Integral Guidance, an image-guidance system. This identifies ocular surfaces and establishes safety zones so the surgeon can decide on a custom, precise treatment. Further, the devices controls are designed with the patient, surgeon, technician and nurse in mind, the company says.

In September 2012, the FDA approved the Catalys for capsulotomy, lens fragmentation, corneal arcuate incisions and corneal primary incisions and sideports.

► VICTUS. The VICTUS platform, from Bausch + Lomb, Technolas Perfect Vision GmbH, supports cataract and corneal procedures on a single platform. It received CE mark approval in Europe in November 2011 and has been used in more than 2,000 cataract or refractive procedures around the world. The VICTUS platform is FDA-cleared for the creation of a corneal flap in patients undergoing LASIK or other treatments requiring initial lamellar resection of the cornea and anterior capsulotomy during cataract surgery. The company says it plans to submit additional indications to the FDA.

There can be some challenges associated with femtosecond laser cataract surgery. There can be air bubbles in the anterior chamber, smaller bubbles around the capsulorhexis edge and larger gas pockets in and around the lens nucleus. Also, femtosecond laser procedures require patients to be fully cooperative so they do not break vacuum. In addition, laser angle is key when performing this procedure. If the laser is misaligned by even a fraction of a millimeter, the energy delivery can be misdirected with unexpected results, such as a partially completed capsulorhexis.

The importance of a well-centered and precisely formed capsulorhexis is critical today because of the emerging premium IOLs market. With both accommodative and multifocal IOLs — particularly those that are pupil dependent — the performance of the lens can be dampened by an irregular or decentered capsulorhexis. The size of the capsulorhexis is also very important in optimizing the performance of accommodating IOLs.²

Corneal applications

The femtosecond laser has made a foothold in the ophthalmic anterior segment arena because of the versatility of its use. Currently, there is a study of intrastromal astigmatic keratotomy (ISAK) being performed outside the United States. Unlike the penetrating consequences of an astigmatic keratotomy, ISAK may reduce postoperative discomfort, symptoms of dry eye and the risk of infection. The emerging consensus is that the greatest role of the femtosecond laser for astigmatic correction will be in eyes with up to 1D-to- 1.5D of cylinder.¹

The corneal applications of femtosecond lasers and the status of the current technology:

► Presbyopia. Technolas PerfectVision and LensAR have developed femtosecond treatments for presbyopia. The Technolas approach, IntraCor, looks to improve near vision in emmetropic hyperopes by a process of flapless intrastromal corneal reshaping. In a 2012 study, results from a prospective, multi-center clinical trial, which included 63 patients who underwent the IntraCor procedure, reveal all eyes attained corrected distance visual acuity of 20/40 or better, and 25% of eyes gained one-to-three lines. However, 21.4% of eyes lost one line and 7.1% lost two lines of corrected distance visual acuity. At near, 70.7% of the eyes attained a Snellan visual acuity of 20/40 or better. All eyes gained uncorrected near visual acuity and 3.4 % of eyes improved nine lines.³

► Myopia/myopic astigmatism. The VisuMax laser, from Carl Zeiss Meditec, corrects myopia and myopic astigmatism. The Femtosecond Lenticule Extraction (FLEx) procedure involves the intrastromal creation of a refractive lenticule that is then removed through a small (3mm-to-5mm) incision.⁴

► Corneal inlays. This intrastromal aspect of the femtosecond laser has also been used to make a pocket for corneal inlays. In clinical trials, lenses, such as AcuFocus's Kamra pinhole lens, Revision Optics PresbyLens and Presbia's Flexivue Microlens, all require a small pocket to settle inside the cornea. The femtosecond laser can provide the precise size and depth, leading to better visual acuity and less potential for complications.

► Deep anterior lamellar keratoplasty (DALK)/descemetstripping endothelial keratoplasty (DSEK). Intralase (Abbott Medical Optics) realized the clinical implications of femtosecond technology early on and attempted to use the laser for numerous corneal procedures outside refractive surgery. Working on pig eyes and cadaver eyes, the femtosecond laser was demonstrated to be effective in DALK and DSEK. The precision of the corneal cut in these penetrating keratoplasties has proven to be a formidable replacement to the full-penetrating surgeries.⁵

► Keratoconus. Femtosecond lasers also enable keratoconus stability. The laser creates a channel for intrastromal corneal rings. As a result, patients can regain visual acuity faster. The intrastromal ring segments work by flattening the steep cornea, and the process can be strengthened with the infusion of riboflavin.

The femtosecond laser may prove useful in this process as well: Corneal collagen crosslinking (CXL), with the use of riboflavin, is designed to help strengthen an already weakened cornea and can retard the progression of sight-threatening visual diseases and potentially hold off a possible corneal transplant.

► Collagen cross-linking. Traditional CXL has been done with insertion of riboflavin drops on a cornea that has had the epithelial tissue removed.

Anastasios Kanellopoulos, M.D., reported 10 cases of early keratoconus patients treated with CXL using an intrastromal pocket created by the Intralase FS60 femtosecond laser. The nasal hinge pocket had a 100-µm corneal depth, 7mm diameter centered at the pupil and a 10º temporal side cut.⁶

The femtosecond laser corneadissection step, performed on the ectatic cornea, may raise concern for further biomechanical destabilization. There is growing evidence that in a femtosecond laser-created flap, it is the final side-cut that changes the corneal biomechanics and not the lamellar corneal separation (pocket). Dr. Kanellopoulos feels that the creation of a pocket with just a 10° side-cut at the 7mm diameter may minimize this concern. The advantage of this model appears to present less pain and faster visual recovery for the patient than an epithelial-off procedure.^3,6

Moving forward

Technology continues to move the surgical procedures toward more precise and predictable outcomes. The femtosecond laser is a perfect example of the innovative and creative ways lasers can help our patients. The automated nature of all these procedures benefits the patients as well as making the post-operative treatment free of sequel. OM

1. Kessel L, Eskildsen L, van der Poel M, Larsen M. Non-invasive bleaching of the human lens by femtosecond laser photolysis. PLoS One. 2010 Mar 16;5(3):e9711Intrastoml femtosecond astigmatic keratotomy promising. Ophthalmology Times. April 23, 2012.
2. Masket S, Sarayba M, Ignacio T, Fram N. Femtosecond laser-assisted cataract incisions: architectural stability and reproducibility. J Cataract Refract Surg. 2010 Jun;36(6):1048-9.
3. Holzer MP, Knorz MC, Tomalla M, Neuhann TM, Auffarth GU. Intrastromal femtosecond laser presbyopia correction: 1-year results of a multicenter study. J Refract Surg. 2012;28(3):182- 188.
4. Shah R, Shah S, Sengupta S. Results of small incision lenticule extraction: All-in-one femtosecond laser refractive surgery. J Cataract Refract Surg. 2011 Jan;37(1):127-37.
5. Mehta JS, Shilbayeh R, Por YM, et al. Femtosecond laser creation of donor cornea buttons for Descemet-stripping endothelial keratoplasty. J Cataract Refract Surg. 2008 Nov;34(11):1970-5.
6. Kanellopoulos AJ. Collagen crosslinking in early keratoconus with riboflavin in a femtosecond laser-created pocket: initial clinical results. J Refract Surg. 2009 Nov;25(11):1034-7.

Dr. Bloomenstein currently practices at Schwartz Laser Eye Center in Scottsdale, Ariz. He is a founding member of the Optometric Council on Refractive Technology. Dr. Bloomenstein has no financial interest in any products discussed. E-mail him at mbloomestein@gmail.com, or send comments to optometric management@gmail.com.