ocular surface & dry eye
Mechanical microkeratomes continue refinements

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A majority of surgeons continue to rely on the traditional flap-cutting tool that offers increasing precision

LASIK flaps created by the finely honed steel of mechanical microkeratomes continue to appeal to the majority of refractive surgeons, even as femtosecond laser use has grown in recent years. And surgeons who use the more traditional mechanical blades can benefit from the greater precision of modern microkeratomes.
Karl G. Stonecipher, M.D., medical director, TLC Laser Eye Center, Greensboro, N.C., co-medical director, TLC, Raleigh, N.C., noted that both mechanical keratomes and femtosecond lasers have improved in recent years. Specifically, mechanical keratomes have improved both the quality of blades they offer and they feature tighter specifications.
“Some of the newer mechanical microkeratomes are making more planar flaps like the femtosecond lasers,” Dr. Stonecipher said.
Improvements in the precision manufacturing of mechanical blades have aimed to reduce the incidence of unexpectedly thick flaps, partial flaps and flaps with variable thicknesses, which can affect LASIK complication rates.
Mechanical keratome improvements have sought to build on some of the advantages of the older mechanical approach to flap creation, including the quicker flap creation than femtosecond systems, which minimizes the amount of time the eye is under suction. Longer suction times can increase the small possibility of permanent damage from induced ischemia.
Steve Khachikian, M.D., cornea fellow, Albany Medical College, Albany, N.Y., uses the LSK Evolution system (Moria, Antony, France) with reusable heads in his Descemet-stripping automated endothelial keratoplasty (DSAEK) and anterior lamellar keratoplasty procedures. Dr. Khachikian uses the mechanical microkeratome to cut his own DSAEK buttons.
Among refractive patients, Dr. Khachikian has used the One Use Plus system (Moria), which is one of the newer single-use mechanical systems that have gained popularity in Europe among tightening sterilization regulations. The single-use approach allows surgeons to forgo expensive and time-consuming upgrades in their sterilization equipment.
Another recent addition to available mechanical microkeratomes systems is the Zyoptix XP platform (Bausch & Lomb, Rochester, New York). This system allows surgeons to create both stromal and epithelial flaps and aims for consistent and repeatable flap thickness.

Competition increases

The appeal of mechanical microkeratomes has decreased in recent years as more report moving toward femtosecond systems. The 2008 ASCRS survey reported that 33% of surgeons use a laser system to create their flaps. However, mechanical microkeratomes continue to dominate with 66% of U.S. surgeons report relying on that technology.
The comparative cost is frequently cited as the chief reason surgeons choose to remain with mechanical microkeratomes instead of newer laser systems. Femtosecond systems generally cost several hundred thousand dollars, while mechanical microkeratomes systems can cost as little as 10% of the price of their femtosecond cousins.
But the survey reveals that the price may be a shrinking obstacle for more surgeons.
The growing popularity of femtosecond laser systems stems from several large studies that have shown that the laser platform produces flaps with greater stability with more consistent and accurate dimensions than the mechanical microkeratome.
Complications that can arise with mechanical microkeratomes include partial or irregular flaps, buttonholes, and free flaps, especially among older patients, those with pre-op hyperopia and patients who have worn contacts for many years.
“Femtosecond flaps continue to look better and better in every way to me except cost,” said Richard L. Lindstrom, M.D., adjunct professor emeritus, Department of Ophthalmology, University of Minnesota, Minneapolis, and founder, Minnesota Eye Consultants, Minneapolis. Dr. Lindstrom avoids button holes when using the Hansatome microkeratome (Bausch & Lomb, Rochester, N.Y.) by not using a plate of less than 130 microns. However, in thin cornea cases, patients with high brows, very flat or steep corneas, a filter bleb, significant pterygium, or any conjunctival edema Dr. Lindstrom always uses the Intralase (Abbott Medical Optics, Santa Ana, Calif.).
Other conditions and patient-types in whom it is best to avoid the use of mechanical microkeratomes, according to Dr. Stonecipher, are those with particularly flat or steep corneas and eyes with epithelial basement membrane dystrophy.
Not all research has identified significant complication-related problems. Recent data presented at the 2009 American Society of Cataract and Refractive Surgery Annual Symposium and Congress reported that flap creation with the new One Use-Plus microkeratome was similar to femtosecond flap creation for sub-Bowman’s keratomileusis. Gustavo E. Tamayo, M.D., the author of a 20-eye study, said flap creation with the mechanical microkeratome had highly reproducible thinness of about 100 microns with a high-quality stromal bed.
An important point that many researchers note is that studies generally find no significant difference in final visual outcome between mechanical microkeratome patients and those treated with femtosecond systems.
This fact is why Dr. Lindstrom still uses mechanical microkeratomes in a small number of patients who request the option and who have no contraindications. Such requests are usually related to the lower per procedure cost for mechanical keratomes.
Some other advantages of mechanical microkeratomes are that they do not require patients to be moved from one device to another and they do not produce the short-term inflammation associated with laser keratomes.

Tips for success

Avoiding complications and achieving the best results with mechanical microkeratomes is closely linked to adherence with the manufacturers’ use and cleaning guidelines, which are very specific to each type of mechanical microkeratome.
But a general rule to help achieve the best outcomes for any mechanical keratome, according to Dr. Stonecipher, is to use the highest quality blades available and to use new blades on each patient. “Also keep the keratome regularly maintained just like routine service on your car,” he said.

Editors’ note: Drs. Stonecipher and Khachikian and Stonecipher have no financial interstests related to this subject. Dr. Lindstrom has financial interests with Abbott Medical Optics (Santa Ana, Calif.).

Contact information

Khachikian: Stevekmd1@gmail.com
Lindstrom: 612-813-3633, rllindstrom@mneye.com
Stonecipher: 336-288 8523, stonenc@aol.com