Mechanical microkeratomes maintain place in surgery

May 15, 2006

Barranquilla, Colombia-Mechanical microkeratomes have anumber of advantages compared with the femtosecond laser"macrokeratome" and should continue to be regarded as safe andefficient instruments for LASIK flap creation, according to CesarA. Carriazo, MD.

Barranquilla, Colombia-Mechanical microkeratomes have a number of advantages compared with the femtosecond laser "macrokeratome" and should continue to be regarded as safe and efficient instruments for LASIK flap creation, according to Cesar A. Carriazo, MD.

"Compared with the laser, mechanical microkeratomes are smaller, cheaper, faster, and more patient-friendly, and they are also flexible, versatile, and have passed the test of time," said Dr. Carriazo, scientific medical director, Carriazo Ophthalmological Center, Barranquilla, Colombia.

"The femtosecond laser is higher technology, but higher technology is not necessary for LASIK flap creation. Therefore, the femtosecond laser should be considered a complement to mechanical devices in refractive and other forms of corneal surgery, but not a replacement," he added.

"By changing the head and blade design, we have had no problems with buttonholes. The suction ring has also been improved so the procedure can be performed with lower suction," Dr. Carriazo said.

Technologic advantages

He acknowledged that the femtosecond laser offers more flexibility than mechanical microkeratomes for customizing features of the flap, including flap diameter, hinge size and position, and flap thickness. In addition, reproducibility of thickness as well as centration and size is better with the femtosecond laser, and it has utility for a broader range of lamellar procedures. However, with respect to refractive procedures, a mechanical microkeratome can be used to perform epiLASIK, LASEK, LASAK, and LASIK, while the femtosecond laser can be used only for the latter two procedures.

In addition, flap thickness reproducibility with modern mechanical microkeratomes is still very good.

"In various comparative studies, the standard deviation for mean femtosecond laser flap thickness ranged from 11 to 15 μm with an average of ±14 μm, but with mechanical microkeratomes the standard deviation range was 12 to 24 μm with a mean of ±19 μm," Dr. Carriazo said.

Dr. Carriazo also presented data to show that overall complication rates are similarly low with the femtosecond laser and mechanical microkeratomes. Considering the most common events, including diffuse lamellar keratitis (DLK)/photophobia syndrome, slipped flap/microstriae, epithelial ingrowth, epithelial defect, and other possible causes of an unsatisfactory flap, the total complication rate was 2.5% for the laser and 2.6% for the mechanical microkeratome.

DLK/photophobia occurred less often with the mechanical device, while epithelial defects and unsatisfactory flaps were less of a problem with the femtosecond laser, and there was essentially no difference between the devices with regard to rates of slipped flap/microstriae and epithelial ingrowth.

"Safety depends on the experience of the surgeon and, with a skilled operator, the rate of complications for both is low, while there can be a high rate of complications with the femtosecond laser in the hands of an inexperienced surgeon," Dr. Carriazo said. "Furthermore, it is still unclear whether there might be some long-term safety issues, including retinal damage, associated with the femtosecond laser."

Lifting flaps

He also pointed out that lifting of femtosecond laser-created flaps is more difficult than lifting of a blade-created flap.

"The dissection plane created with the femtosecond laser is defined by a series of connected plasma bubbles, and because there is some residual tissue between the bubbles, lifting a femtosecond laser-created flap is like tearing Velcro," he said.

From the patient's perspective, the mechanical microkeratome procedure is associated with greater comfort intraoperatively (since there is no need to move) and postoperatively along with faster visual recovery. In addition, a mechanical microkeratome procedure has economic advantages considering the per-procedure cost of the laser and the need for a maintenance contract.