FEMTOSECOND LASERS

While most surgeons agree that the femtosecond laser will ultimately change the face of cataract surgery, its impact on clinical outcomes and its cost-effectiveness in daily clinical practice are still open to discussion, stressed two surgeons in a debate held during the World Ophthalmology Congress. For Zoltan Nagy MD, the first surgeon to perform femtosecond laser cataract surgery, the benefits of the technology are all too apparent. “With the femtosecond laser, there are multiple steps of lens surgery which can be planned and guaranteed. There is better centration of the capsulotomy, it makes capsulorrhexis creation more predictable, and it is effective in liquefying up to grade two cataracts. It can create any type and size of corneal wound, and there is better lens position, and lens centration with this technology. It also delivers better quality of vision, with less higher order aberrations, reduced endothelial cell damage and less cystoid macular oedema following surgery,†he said.

Nevertheless, Dr Nagy, professor of ophthalmology at Semmelweiss University, Budapest, is quick to give short shrift to the idea that the femtosecond laser will sound the death knell for traditional phacoemulsification. “I am often asked if the femtosecond laser will replace phacoemulsification. The answer is certainly not, but it will improve it by converting a manual multi-step, multi-tool procedure into a predictable and consistent surgical technique,†he said. Dr Nagy also dismissed the idea that the advanced automated technology of the femtosecond laser represents a potential threat to the primacy of the surgeon at the heart of the medical process. “Ophthalmologists cannot be replaced by ophthalmic technicians no matter how good the technology is. Surgical experience and wisdom are still needed and even more so than before. Femtosecond cataract surgery is a rapidly developing new technology which will play an increasingly important role in the future, both in refractive lens exchange and in cataract surgery,†he said. Looking at complications associated with phacoemulsification cataract surgery, Dr Nagy pinpointed three potential sources of problems: the corneal incision, capsulotomy and lens fragmentation. “Corneal incisions can have a refractive impact in terms of induced astigmatism and the risk of infection also needs to be kept in mind. The capsulorrhexis is also a potential source of error, especially with the precision required for the latest premium lenses. For the capsulotomy, posterior capsule opacification or even vitreous loss may result if it is not performed correctly. Similarly, errors in lens fragmentation may result in delayed visual recovery, loss of endothelial cells or even corneal decompensation,†he said.

Rigorous patient selection is important to obtain optimal outcomes with the femtosecond laser, said Dr Nagy. Patients with small and non-dilating pupils should be excluded from surgery, while relative contraindications include patients on anti-coagulation therapy, white cataracts and very brown or black cataracts. 'In white tumescent cataracts the femtolaser is very useful in creating capsulorrhexis. In mature cataracts femtolaser is also useful performing the rhexis and the role of femtolasers in fragmentation of the crystalline lens is still under investigation,' Dr Nagy said. In several studies carried out by Dr Nagy, femtosecond laser-assisted surgery using the LenSx laser (Alcon) was shown to deliver enhanced surgical accuracy and reproducibility compared to manual methods. All anterior capsulotomies achieved accurate centration and intended diameter, with no radial tears or adverse events. Corneal incisions were also highly reproducible, with precise dimensions and geometry. Dr Nagy noted only 10 per cent of manually created capsulorrhexis achieved a similar diameter accuracy of +/-0.25 mm as the LenSx laser. Furthermore, there was significantly better IOL centration and a better anterior capsule-IOL overlap in the femtosecond laser group compared to the manual CCC control group. Fewer higher order aberrations and an improved postoperative quality of vision were also found with the LenSx treated patients.

In praise of phaco

While femtosecond lasers are a clear technological breakthrough with exciting potential, it is still too early to write the obituary for traditional phacoemulsification, according to Yehia Mostafa MD. “Phacoemulsification remains a great technology that has proven itself over many years. It is reproducible and unlike the femtosecond laser it can be used for any type or grade of cataract or any pupil size. It can even be used on unclear corneas. It is a machine that is affordable and which gives the surgeon the control he or she needs to deliver excellent results for their patients,†he said. Dr Mostafa, professor of ophthalmology at Kasr Al Aini Faculty of Medicine of Cairo University, Egypt, said that ongoing advances in phaco technology allied to new IOL designs were raising the bar in terms of clinical outcomes for cataract patients. 'Corneal incisions less than 2.4mm are astigmatically neutral and still we can go as small as 1.8mm incisions. Tight, well constructed, well hydrated wounds avoid the risk of infections.

'Manual capsulorhexis is well established and very reproducible once rules are followed allowing proper centration. Decreased posterior capsule opacification is achieved with overlapping edges of anterior rhexis over the optic periphery as proved by various studies together with the material and edge design of the IOL optic. “The short operation time during phacoemulsification, five to 10 minutes, decreases the risk of contamination. And the avoidance of anterior chamber fluctuations decrease vitreous movements and consequently cystoid macular oedema. Using one machine and one microscope for a properly planned surgery makes it easier for the surgeon and patient with less chance of pitfalls,†Dr Mostafa said.

Improved fluidics

“Phaco technology has matured over the years and we now have better safety and efficiency through better power modulation and improved fluidics. This decreases the amount of energy being delivered into the eye and protects the corneal endothelium. Nuclear cataracts one and two almost require no power at all and it is a mere phacoaspiration. The introduction of torsional or transverse phacoemulsification has also enabled us to emulsify almost any type of nucleus with less risk to the cornea and the posterior capsule,†he said.

Dr Mostafa said that one of the advantages of traditional phacoemulsification is its versatility. “Even with compromised corneas, small pupils, extremely mature cataracts and posterior subcapsular cataracts, it is still possible to perform a proper capsulorrhexis, to easily remove the nucleus with the least impact on the corneal endothelium thanks to the newer modalities of power modulation and fluidics and improved techniques,†he said. There is no contraindication for conventional phacoemulsification except total corneal opacity or total subluxation of lens. Summing up, Dr Mostafa said that phacoemulsification remains a tried, cost effective and trusted technology that is continuing to deliver excellent clinical results for patients worldwide.