New Carriazo-Pendular microkeratome improves LASIK flap standards

A spherical molding system and pendular blade oscillation produce high-quality flaps in any quadrant of the cornea.

Issue: September 1, 2002

ByMichela Cimberle

BARRANQUILLA, Colombia — With a new approach to flap-making, the Carriazo-Pendular microkeratome performs high quality flaps of variable size and orientation, using less suction than any other microkeratome on the market, according to its developer.

“The head does not use an applanation plate, but a spherical molding system, which gradually increases the pressure when the head starts cutting the flap (figure 1). The blade is curved along a meridian, and advances with a pendular oscillation movement that performs a smooth cut. The spherical molding system is located in front of the blade, at a distance that remains constant during the cut, to produce discs of uniform thickness,” said Cesar Carriazo, MD.

Options

The Carriazo-Pendular, manufactured by Schwind eye-tech solutions, offers a series of options regarding disc diameter, hinge position and action mode.

Suction rings come in various sizes to perform flaps between 8 mm and 11 mm in diameter to suit all eye shapes and sizes. They are marked as 9.0 left and right and 10.0 left and right.

The Carriazo-Pendular microkeratome (right) has a spherical molding system rather than an applanation plate as in most microkeratomes (left).

“The special design of the suction rings offers a much larger vacuum chamber for better suction (figure 2) and allows making cuts in a range of sizes, down to small ones. The choice depends on the patient’s keratometry and on the programmed ablation diameter,” Dr. Carriazo said.

The cut can be performed in all directions, starting from any of the four quadrants: down-up, lateral-lateral and oblique.

“This is one of the systems that can really be used that leaves the hinge in any quadrant of the cornea, as there are no obstructions in its path. A preset stop is located on the lateral support of the ring, to stop the microkeratome head according to the hinge size,” he said.

Surgeons can choose between automatic or manual mode for cutting the flap, and the head has different pendular drivers for each mode. All rings can be used for manual or automatic advance.

“The manual system gives the surgeon more direct control over the procedure. If the advance movement is at a high speed, a thinner disc is obtained than if the advance movement is performed with a slow, even movement. The motor is needed only during the cut, and it is switched off during the reverse movement,” he said.

Although the system has been designed to be used with the same hand operating on both eyes, the set comes with right and left rings for surgeons who prefer changing hands between the two eyes.

The spherical head gradually increases pressure (center right) while the cut is performed. Suction problems produce irregular cuts in the periphery (far right) rather than in the center.

Smooth cutting

Another characteristic of the microkeratome head is the absence of external gears. Instead, there are round guides on the sides, which are designed to couple with similar guides in the suction ring for stability during the advance movement.

“There is a minimum but stable contact between head and ring, which allows for a smooth sliding movement, maintaining the correct position without friction,” Dr. Carriazo said.

“The head gradually increases in pressure while the cut is performed, pressing 0.5 mm more in the center than in the periphery,” he said. “In this way, the flap is protected from central holes in case of suction problems, which is a risk with other microkeratomes (figure 2). With the Pendular, suction problems produce irregular cuts in the periphery rather than in the center, which is less of a risk for the patient.”

The suction ring of the Carriazo-Pendular offers a vacuum chamber than conventional microkeratomes for better suction.

A safe system

Power is supplied by two electric motors with two separate axes. One motor rotates at 12,000 rpm (variable from 8,000 to 15,000 rpm) and activates the blade’s oscillation. The second motor advances the blade at 4 mm/sec (variable from 2 to 6 mm/sec).

“In the automatic mode, the advance motor moves the gear freely while the head is not engaged in the ring. As soon as the head engages the lateral supports of the ring, the driver is blocked and the system oscillates around it, generating the pendular advance movement,” Dr. Carriazo explained.

The power unit provides electrical energy to the motor and the vacuum for the suction ring through a vacuum pump. The unit has several safety devices, including an alarm system in case of vacuum loss. An automatic test of the pump and vacuum valve is activated as soon as the console is switched on.

The calibrated vacuum must reach a preset pressure within a defined time limit, and the pressure has also to be released within a defined time limit. The cutting procedure can only be performed once the test has been successfully completed, Dr. Carriazo said.

The system comes with right and left rings for surgeons who prefer switching hands between eyes.

Cuts can be performed in any direction with the Carriazo-Pendular microkeratome.

For Your Information:

Cesar Carriazo, MD, can be reached at Calle 86 No. 49C-69, Barranquilla, Colombia; (57) 5378-6332; fax: (57) 5378-6332; e-mail: ccarriazo@hotmail.com. Ocular Surgery News could not confirm whether Dr. Carriazo has a direct financial interest in any of the products mentioned in this article, or if he is a paid consultant for any company mentioned.

Schwind eye-tech-solutions, distributors of the Carriazo-Pendular microkeratome, can be reached at Mainparkstrasse 6-10, 63801 Kleinostheim, Germany; (49) 6027-508-0; fax: (49) 6027-508-208; Web site: www.eye-tech-solutions.com.