Combating cataracts with lightsabers

Guided by 3-D imagery, femtosecond lasers can slice up a cloudy lens with more precision and fewer nicks and tears.

Guided by 3-D images of live eye tissue, lasers now allow ophthalmologists to conduct cataract surgery with more precision than ever.

A cataract clouds the lens of your eye, causing you to see the world from behind a frosted glass or waterfall (where it gets its name). Cataract surgery to correct this mostly age-related condition is the most frequently performed surgical procedure in the US. One-third of Americans will likely undergo the surgery in their lifetime.

A team of researchers led by Stanford ophthalmologist Daniel Palanker combined a 3-D imaging technique with the precision of a laser – such as in LASIK, which corrects nearsightedness in millions of people a year.

Presently, important steps of the procedure are manual – a dexterous surgeon cuts an opening in the capsule that surrounds the cloudy lens, removes the fragment, and implants a plastic one – controlled by freehand pulling and tearing (examples of manually cut lens pictured on top, laser-cut on the bottom).

To guide the laser, the team uses optical coherence tomography, which creates 3-D images of live tissue using light scattered by structures within the eyes. With a 3-D map of the eye, the instrument calculates the exact placement, precise sizing, and shaping of the cutting patterns for cataract removal, and then directs the laser to execute these slices.

The femtosecond laser uses light pulses that zap a focal spot, turning it into quickly-dissipating plasma without accumulating heat or harming surrounding tissue. It cuts a circle in the lens capsule, slices the cloudy lens into smaller easy-to-remove pieces, and carves an incision into the cornea for insertion of the replacement lens later (pictured below).

Together, the optical coherence tomography and the femtosecond laser cuts 12 times more precisely than the traditional method – allowing a better fit for the artificial lens.

“This new approach could make this procedure less dependent on surgical skill and allow for greater consistency,” said Palanker.

The team experimented with pig and human eyes from eye banks and then six live Dutch belted rabbits before performing cataract surgery on 50 human patients in a clinical study.

While the researchers found that the new procedure sharpened vision more than the manual way, the improvement wasn’t statistically significant. The study was funded by ophthalmic device company OptiMedica Corp., who calls this the Catalys Precision Laser System. The data will be submitted to the FDA for consideration, and OptiMedica CEO and president Mark Forchette told Bloomberg that he expects the device to be available next year.

However, this method takes longer than the current standard and would cost more, with Medicare unlikely to cover it in the immediate future, “but there will be people who elect to have it done the new way if they can afford it,” said Palanker in a Stanford statement. “There are competitors coming out with related systems. This is what's exciting. This technology is going to be picked up in the clinic.”

The results were published today in Science Translational Medicine. “A lightsaber fares better against the Dark Force than does a metal sword,” the journal’s editor analogized. “Ophthalmologists, who battle the darkening forces of eye disease, have also learned this lesson, replacing steel scalpels with lasers for creating precise, controlled incisions in the eye.”

Images: Science/AAAS

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