New Procedure May Transform Treatment of Cataracts

Dr. Timothy B. Cavanaugh sat at a small table in the San Juan Capistrano office of Optex Ophthalmologics Inc., a detached pig eye staring up at him through the microscope. With deft movements he cut a small slit in the periphery of the eye, punched a hole in the lens and sucked out its jello-like contents using a newly developed probe--all in less than five minutes.

“That was the easiest cataract I’ve ever removed,” said Cavanaugh, an experienced surgeon from the Hunkeler Eye Centers in Kansas City, Mo.

Next was Dr. Michael E. Sulewski of the University of Pennsylvania Medical Center, who repeated the process on another eye. “This is the most important advance in ophthalmology since the development of laser keratotomy,” he said after finishing.

The object of their admiration was a new Optex instrument for performing cataract extractions that, even though it has not yet been tested in humans, holds promise for revolutionizing cataract surgery.

The new procedure, called Catarex, is not only quicker, cheaper and less traumatic than phacoemulsification, the current gold standard for cataract removal, it also requires far less skill on the part of the surgeon, said chemical engineer John T. Sorenson of Optex, one of its inventors.

Surgeons generally practice on at least 50 animal eyes before they are comfortable performing phaco, as it is generally called, on patients. Cavanaugh and Sulewski mastered Catarex the first time with just a little coaching, although both said that they would want to try it a few more times before operating on a patient.

“This is going to take cataract surgery from the hands of the most skilled surgeons and allow everyone to do it,” Sulewski said. Optex hopes to have completed clinical trials and have it on the market by the end of next year.

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Cataracts occur when proteins inside the normally clear lens begin to clump together, becoming opaque and blocking vision. The most common cause is simple aging, but they can also be produced by long-term exposure to ultraviolet light in sunshine, by diabetes, steroids and injuries to or surgery on the eye.

More than half of all Americans older than 65 have a cataract, and untreated cataracts remain a leading cause of blindness.

The only treatment for cataracts is surgery, which entails removing the cloudy lens. Vision can then be restored by inserting a foldable plastic lens in its place or with special glasses or contact lenses.

About 1.4 million cataract surgeries are performed in the United States each year. At an annual cost of $3.4 billion, such surgeries represent the largest single expenditure by Medicare.

More than 90% of all patients who undergo cataract surgery have better vision afterward, according to the National Eye Institute. The success rate climbs to 98% among patients who have no complicating factors, such as glaucoma or diabetes.

There are currently two ways to remove cataracts, phaco and a conventional surgical approach called extracapsular cataract extraction or ECCE. In ECCE, a quarter- to half-inch (6-11 mm.) incision is made in the eye, the front of the lens capsule is cut away and the lens is lifted out intact.

ECCE takes about 30 to 45 minutes. One of the most common complications is significant astigmatism (distortion of the shape of the cornea) caused by scarring of the large incision site.

Phaco, developed about 10 years ago and now much more common than ECCE, is less intrusive, using an incision that is less than a quarter of an inch long (3-5 mm.). As in ECCE, the front of the lens membrane is cut away and the surgeon inserts a small ultrasonic probe.

Using the probe, the surgeon chisels away the lens, which is suctioned out by the probe while saline solution is pumped in. A second tool may also be used to remove the remaining bits of the lens.

A plastic lens is then inserted. The entire procedure takes 20 to 30 minutes. Because the incision is smaller, phaco is less traumatic than ECCE and there is less post-surgical astigmatism.

But there are risks: Stray ultrasonic energy from the probe can damage the delicate endothelial cells lining the cornea, necessitating a cornea transplant. The probe itself can also heat up, burning the incision site.

Most important, Sulewski noted, the surgery requires a high skill level to prevent subsidiary damage. Surgeons performing phaco often have very high blood pressure during the procedure because of the tension and skills involved, he said. Some surgeons, he added, use ECCE instead to avoid the stress.

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By contrast, Catarex requires only limited skill. A special probe developed by Sorenson, physicist Michael Mittelstein and bioengineer Soheila Mirhashemi of Optex is inserted into the lens through a 1.5- to 2.5-mm. incision in the eye and held stationary. The probe itself does all the work.

The key is a special impeller--a miniature set of blades much like the propeller on a motorboat--that, when rotated at up to 55,000 rpm, creates a vortex in the lens.

The vortex is, in effect, a miniature tornado that breaks up the lens and sucks it out without disturbing the lens capsule. The probe requires only 30 seconds to two minutes to extract the lens, and the entire procedure takes less than 15 minutes.

“This is the kind of operation a general ophthalmologist could do instead of requiring a highly skilled surgeon,” said Dr. Ellen Lieberman of the National Eye Institute, which partly funded its development.

When Catarex surgery is first performed in humans, surgeons will replace the lens with a rigid plastic one, as is done now for phaco and ECCE. But eventually, the researchers hope that the emptied lens membrane can be filled with a flexible polymer that could be focused by muscles in the eye just like the natural lens is.

Several companies are working to develop such materials and Catarex “is an enabling technology that would make it possible to use them,” Sorenson said.

The process has been studied in isolated pig eyes and in live pigs by Dr. Alan P. Kratz of UC Irvine. “This could offer us a uniform and rapid way of removing cataracts,” he said.

But first it has to be tested in humans. Because the Food and Drug Administration considers it a variant of phaco, such trials could require as few as 30 patients, according to J. D. Lindjord, president of Atlantic Pharmaceuticals Inc., Optex’s parent company. Those trials could be concluded early next year, he said.

Easier on the Eye

A new surgical technique for removing cataracts, called Catarex, is quicker, safer and requires much less training on the part of surgeons.

Phaco

A small probe uses ultrasonic energy to chisel away the lens material so it can be suctioned out. The process is very skill-intensive; stray energy from the probe can damage the cornea, and the hot probe can burn the eye.

Catarex

In Catarex, the surgeon cuts a smaller hole in the eye, then uses a special tool to make a round hole in the lens. A special probe is inserted into the lens. A propeller-like impeller in the probe rotates at up to 55,000 rpm, creating a vortex that breaks up the lens and sucks it out. The technique is easily learned and seems to have few complications.

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Source: Optex Ophthalmologists Inc.