LASERS FOR CATARACTS

The idea of using lasers to emulsify cataracts is nothing new, but in fact goes back over 30 years to a time when ECCEs accounted for most cataract surgeries, said Lucio Buratto MD who presented his personal perspective on the development of laser-assisted phaco at Femto 2013, an international meeting on anterior segment surgery.

“Over the years of my surgical life I've had many wonderful experiences and one of the best has been to participate in the evolution of lasers for performing cataract surgery,” said Dr Buratto, Milan, Italy.

He noted that the original idea of using a laser was to perform a capsulorhexis and/ or emulsify the lens from the outside of the eye. The earliest use of lasers in relation to cataract surgery was in 1982 when Franz Fankhauser performed the first laser posterior capsulotomy on a human patient with a neodymium: yttrium aluminium garnet (Nd:YAG) laser. The indication for treatment in this case, as in most cases today, was a posterior capsulotomy to remove posterior capsule opacification.

Dr Fankhauser had worked closely with Danièle Aron-Rosa MD in the development of the Nd:YAG laser. Their research showed that application of the laser in this way was unlikely to damage the surrounding tissue. However, he was reluctant to use the laser out of fear that it might damage the lens. He nonetheless performed the procedure and saw that the lens remained intact, thus beginning a new era in ophthalmic surgery.

The following year, Dr Buratto began using the Nd:YAG laser for performing anterior capsulotomies during cataract surgery. He used the laser to pierce holes in the capsule in the style of a can-opener capsulotomy. However, he found that while it was generally possible to perform an anterior capsulotomy in this way, in many cases there were problems with pupil constriction and there were pronounced anterior chamber reactions. He therefore decided that the bent-needle cystotome anterior capsulotomy technique was better.

A decade later, in 1993, the introduction of picosecond lasers for cataract surgery renewed Dr Buratto’s interest in laser- assisted cataract surgery. Leading the research was Vincenzo Marchi MD in Rome, who demonstrated that it was possible to perform anterior capsulotomy and nucleofragmentation with the laser. Like the Nd:YAG laser and the femtosecond lasers of today, the picosecond laser was designed to perform procedures on the inside of the eye from the outside of the eye.

“I was almost ready to buy a laser but finally I decided not to because it didn't really look all that promising for the future,” Dr Buratto said.

The close of the millennium saw the introduction of several lasers that were designed basically as laser versions of ultrasound phacoemulsification devices. The first to come along was an erbium:YAG laser which had a fibre- optic probe deliver the laser pulses in a non-contact mode to induce photo vapourisation.

Next came the Paradigm Nd: YAG laser which had a wavelength of 1064 nm and like the erbium YAG laser transmitted laser energy through a fibre optic probe. Unlike the erbium:YAG laser, which applied energy directly to the cataract, the Paradigm laser shot its beam at a titanium target to create shockwaves causing optical breakdown and plasma formation.

Unfortunately for the new technology, lasers were still playing catch-up with ultrasound phacoemulsification, which at the time was itself undergoing a steady evolution, with greatly reduced effective phaco times. Therefore, Dr Buratto and most ophthalmologists could not see any advantages in the new lasers.

“One drawback was that they didn't work as well in hard cataracts, which we still were doing fairly frequently back in those days. Nowadays, we mainly treat softer cataracts,” he added.

Finally in 2000, Dr Buratto began using the ruby phaco laser which he said was quite effective in emulsifying cataracts with few complications. However, he became disenchanted with the machine when he had a case where there was a posterior capsule rupture and a dropped nucleus.

“We were initially happy with this machine and we didn't have that many complications, but when I had a case where I lost the nucleus into the vitreous after rupturing the capsule, I realised it had no safety advantages over ultrasound phacoemulsification,” he said.

He noted that the introduction of femtosecond laser-assisted cataract surgery in recent years has brought laser cataract surgery full circle, returning once more to an ab externo technique. This became possible not only because of the lasers themselves, but also because of the concurrent emergence of highly reliable imaging technology, such as Scheimpflug cameras and OCT devices which guide the lasers with extreme precision.

“Femtosecond laser-assisted seems to solve all the problems we had with previous lasers, so I think with this new technology we're moving in the right direction,” Dr Buratto added.