FEMTO-CAT UPDATE

The femtosecond laser’s accuracy and predictability in the performance of capsulotomy and corneal incisions, and the reduction it provides in the need for ultrasound energy can translate into a more accurate and stable positioning of the IOL, improved visual outcomes and less trauma to intraocular structures than is the case with conventional phacoemulsification techniques, according to Zoltan Nagy MD, Semmelweis University, Budapest, Hungary.

“The advantages of femtosecond laser technology include higher safety, higher predictability, less phaco energy, shortened treatment time, better results with premium lenses and significant help in complicated cases like traumatic cataracts, loose zonules, and white and tumescent cataracts,” Dr Nagy said at the 18th ESCRS Winter Meeting in Ljubljana.

In the first clinical study to evaluate the performance of a femtosecond laser (LensX®, Alcon) in cataract procedures, which Dr Nagy and his associates published in 2009 (Nagy et al, J Refract Surg 2009; 25:1053-1060), the results demonstrated that a femtosecond laser can effectively perform corneal incisions, a central and guaranteed diameter capsulotomy and fragmentation and liquefaction of the crystalline lens.

Dr Nagy noted that since that time he and his team have published around 20 studies concerning femtosecond laser-assisted cataract surgery, all using the LensX system. They show that the femtosecond lasers have demonstrated a statistically significant superiority over conventional ultrasound phacoemulsification in several clinical parameters. For example, one study showed that the mean amount by which the capsule overlapped the anterior surface of the IOL at one year was significantly higher in eyes with femtosecond laser-created capsules than in those that had undergone manual capsulorhexis. The study also showed the amount of overlap had an inverse correlation with amount of decentration (Kranitz K et al, J Refract Surg 2011; 27:558-63).

In another study, imaging with a Pentacam Scheimpflug camera supported those findings and also indicated that the mean amount of IOL-tilt was significantly greater in eyes that had undergone conventional phacoemulsification than it was in those that had undergone femtosecond laser-assisted surgery. It also showed that the amount of tilt and decentration had a statistically significant inverse correlation with corrected distance visual acuity (Kránitz, J Refract Surg 2012; 28:259-63).

Results of another study indicate that the superior IOL positioning afforded by femtosecond laser capsulotomy is also reflected in the quality of vision. Aberrometry performed with the NIDEK OPD-Scan II showed that eyes that had undergone femtosecond cataract surgery had significantly lower mean values of tilt and coma, and significantly higher mean Strehl ratios and modulation transfer function (MTF) values than eyes that had undergone conventional phacoemulsification with manual capsulorhexis (Miháltz, J Refract Surg. 2011; 27:711-716).

Recent studies have also shown that the femtosecond laser may be gentler to the eye than conventional phacoemulsification. That is probably the result of the much reduced requirement for phaco power during nuclear fragmentation and emulsification, he noted.

In one study, measurements taken with the Pentacam showed that mean central corneal thickness was significantly greater at day one postoperatively in eyes undergoing standard phacoemulsification (607µm) than in those undergoing femtosecond-laser assisted cataract surgery(580µm). Both groups had similar mean central corneal thickness preoperatively, and at one week and one month postoperatively (Takács, J Refract Surg. 2012; 28:387-391).

In the same study confocal microscopy showed that endothelial cell count was higher in the femtosecond laser group than in the phacoemulsification group, though not statistically significant.

“We found that the postoperative corneal oedema and endothelial damage was less in the femtosecond group than in the manual procedure group. That is especially due to the shorter treatment time and less heating of the aqueous,” Dr Nagy said.

In another study, OCT measurements (Stratus OCT3, Carl Zeiss Meditec, AG) showed significantly less thickening of the inner macular ring in eyes that had undergone cataract surgery with the femtosecond laser than in those that had undergone conventional phacoemulsification (Nagy et al, J Cataract Refract Surg. 2012 Jun; 38(6):941-6).

Dr Nagy noted that femtosecond laser-assisted cataract surgery is a very new technology system, having been in clinical use for only five years. The chief barriers to its wider adoption is its high expense, which includes not only the capital investment in the machines, but also a click fee and a service fee. However, he said it is the technology that will ultimately provide patients with the best results in terms of safety and visual outcomes.

Zoltan Nagy: zoltan.nagy100@gmail.com