FS CATARACT SURGERY

Femtosecond laser-assisted cataract surgery can reduce complications in some of the most difficult cases, presenters told the American Society of Cataract and Refractive Surgeons (ASCRS). Reported benefits of the technology include significant reductions in ultrasound energy and associated corneal damage in very hard, dense cataracts, and prevention of radial tearing when opening intumescent capsules.

In a series of 27 eyes with intumescent cataracts, complete capsulotomies with no adhesions or tears were achieved in 25, or 93 per cent, using a Catalys femtosecond laser (Optimedica), Matthias Elling MD of the University Eye Clinic, Bochum, Germany reported. The remaining two eyes had tags in the capsulotomy, resulting in small tears. However, these did not damage the capsules enough to prevent implantation of intraocular lenses (IOLs) in the bag without complications.

By contrast, manual capsulorhexis in intumescent cataracts often leads to large radial tears, sometimes extending to the posterior, as the pressurised bag tends to burst when punctured, Dr Elling noted. “To prevent capsular tears, safety starts with a precise and fast capsulotomy,” he emphasised. Juan F Batlle MD of the Dominican Republic also reported success treating Morgagnian cataracts with a femtosecond laser. The situation often arises in very elderly patients or those who have received prior surgery for the vitreous or retina where the lens truly becomes a fluid-filled bag as described by Dr Morgagni, he explained.

Surgical management in such cases can be difficult, prompting many to opt for an extracapsular technique or manual small incision cataract surgery to avoid posterior capsule rupture, Dr Batlle observed. “The fear is the so-called Argentinean flag syndrome, in which the blue-stained capsule splits when punctured for capsulorhexis, revealing a white band of nucleus across the entire equator. This often occurs even when the anterior chamber is pressurised,” he said. However, confirmation should be made at surgery that a complete 360-degree capsulorhexis has been performed prior to removal of the capsule so as to avoid radial tears produced by tags or incomplete cuts, Dr Batlle added.

Femtosecond laser technology also helps manage black or rock-hard nuclei, Dr Batlle said. He presented a case in which he was not able to visualise the posterior capsule at the slit lamp due to a dark cataract, necessitating an immersion A-scan to measure axial length. However, at surgery, the laser’s OCT clearly imaged the posterior capsule, enabling softening of the nucleus while maintaining a safety zone. The bubbles released from behind the nucleus during laser pre-treatment help separate the dense cataract from the capsule, Dr Batlle said. The laser also disrupts the leathery surface typically found on cataract nigrans, making it much easier to crack and remove without major injury.

“We began our sojourn with the femtosecond laser in June 2009. I am convinced that the Catalys laser will make the average cataract surgery easier and more precise, the difficult cases become average and those that are virtually impossible become possible,” said Dr Batlle, who is a consultant for Optimedica.

Femtosecond laser lens fragmentation also reduces ultrasound energy for removal of advanced cataracts, Jonathan Talamo MD of Harvard Medical School reported. In a study of 51 cataracts of LOCS grade 5+, with maximum volume fragmented by laser, mean effective phaco time measured 2.22 +/- 2.95 seconds. That time fell between the average phaco times for grade 2 and grade 3 cataracts observed in a comparison group operated by the same surgeons without laser lens fragmentation. The surgeries were done at Burkhard Dick MDs facility at the University Eye Clinic in Bochum, Germany.

So is femtosecond laser energy any better than ultrasound? “Most of us would conclude ‘yes,’” Dr Talamo said. Femtosecond laser softening causes less tissue disruption than phaco, possibly because it produces more but smaller cavitation zones – about 50 microns diameter compared with 600 microns for phaco, Dr Talamo noted. The result is about 1,000 times less collateral damage from cavitation bubbles, and less heat build-up, which reduces thermal damage.

This reduces corneal oedema, endothelial cell loss and intraocular inflammation, making laser energy safer than ultrasound for softening advanced cataracts, Dr Talamo said. “As you would expect from this, the peer reviewed literature is starting to show reduced postoperative recovery time.” Reducing phaco time also reduces surgical time in the eye, which in turn stresses zonules and other tissue less, Dr Talamo noted. Laser pretreatment may also reduce suction requirements and with it irrigation volume and pressure needed to maintain anterior chamber stability during surgery. So should replacing ultrasound phaco with femtosecond laser be the goal? “It is probably achievable. Zero phaco for most is okay, but zero for all will not necessarily achieve better outcomes. But trying to get there will help,” he said.