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Femtosecond laser surgery of the lens: a second revolution?
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 Joseph Colin |
The era of modern cataract surgery began in 1967, with the “phaco revolution” of Charles D. Kelman, MD. The radical changes brought by the use of ultrasound energy were slowly accepted and gradually adopted by the ophthalmic community. With the introduction of flexible implants, phacoemulsification eventually established its position as the state-of-the-art in cataract removal.
Over the following years technology has continued to evolve through incremental improvements, allowing the creation of increasingly smaller incisions.
At the same time, corneal refractive surgery witnessed a gradual switch from mechanical microkeratomes to femtosecond lasers. Ultrashort pulses now enable us to perform very accurate and reproducible LASIK flaps as well as intracorneal tunnels for intracorneal rings, and to carry out better quality keratoplasty procedures, both penetrating and lamellar.
It was obvious that sooner or later we would want to evaluate the possibility of applying femtosecond laser technology to cataract surgery. A femtosecond-assisted procedure, guided by anterior segment imaging (OCT or Scheimpflug), holds the potential for unprecedented precision, reproducibility and safety. Furthermore, it meets the higher requirements of premium IOLs, toric, accommodative and multifocal, creating the conditions in which they can guarantee the best refractive outcomes.
Several stages of the cataract procedure can be assisted by femtosecond laser, starting from inside the eye and reaching the surface: nucleus liquefaction, capsulorrhexis, corneal incision and, when needed, astigmatic relaxing incisions.
Nucleus liquefaction can be applied to cataracts grade 1 to 3 or even up to 4. Microphotolysis is carried out using a variety of dissection patterns, such as four quadrants, multiple concentric circles, microcubes or microspheres. Aspiration is then performed as in conventional phaco. The time the globe stays open is decreased considerably and the trauma caused to the ocular tissue (endothelium, capsule and iris) by ultrasound is entirely avoided.
Femtosecond lasers enable us to perform perfectly centered capsulorrhexes, with custom shapes and sizes. The same level of accuracy would never be achieved by manual techniques. In a study carried out in Budapest by Zoltan Nagy, MD, femtosecond and manual capsulorrhexes were compared in two groups of 60 patients. All laser-performed capsulorrhexes were within +/-0.5 mm of intended diameter. The same result was achieved in only 10% of the manual dissection group. This precision in diameter, size and centration can be crucial when using premium IOLs. Furthermore, in case of weak zonules, surgical stress is considerably decreased. Last but not least, with such a precise match between the anterior capsule and IOL optic, the rate of secondary cataracts is likely to decrease.
A simple step like corneal incision also can be improved by the use of femtosecond laser. Cut geometry and size can be precisely calculated. Roger Steinert, MD, compared femtosecond laser and manual incisions in two groups of eyes. He found that in the femtosecond laser group several incisions did not need sutures or stromal hydration for sealing.
Three companies, LenSx Lasers Inc. (recently acquired by Alcon), LensAR Inc. and Optimedica Corp., are currently investing in femtosecond technology for cataract surgery and have presented the results of their initial series. With all lasers the procedure appears to be extremely promising in terms of increased accuracy, reproducibility and safety compared to conventional surgery.
Nevertheless, in some cases of advanced cataract, the need for ultrasound phaco still persists. It is still early days, and further advances are needed to optimize the efficiency of this new technique.
Although the cost of the procedure is likely to be higher compared to phacoemulsification, femtosecond laser cataract surgery is likely to become the gold standard in the near future. We are witnessing a second revolution that will bring enormous changes to our practice. Because some stages of the procedure need a clean but not necessarily sterile environment, we may be able to move toward shared care, with part of the procedure being carried out by specially trained non-medical staff outside the operating room. This will allow us to increase the volume of cataract procedures, to save medical time and to shorten wait lists.
Because change always stimulates ideas and brings new opportunities, we should expect this technology to open up new and unexplored possibilities. Already, the femtosecond laser platforms for cataract are finding applications in other lens-related, innovative techniques, such as phacophotomodulation to restore accommodation and photolysis to restore crystalline lens transparency. As we have heard many times before, this is an exciting time in cataract surgery, which never ceases to amaze us with its inner potential of expansion and growth.
References:
- Kessel L, Eskildsen L, van der Poel M, Larsen M. Non-invasive bleaching of the human lens by femtosecond laser photolysis. PLoS One. 2010;16;5(3):e9711.
- Nagy Z et al. Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. J Refract Surg. 2009;25(12):1053-1056.
- Schumacher S, Fromm M, Oberheide U, Gerten G, Wegener A, Lubatschowski H. In vivo application and imaging of intralenticular femtosecond laser pulses for the restoration of accommodation. J Refract Surg. 2008;24(9):991-995.