MK-2000 at the cutting edge of blade technology for keratectomy procedures

By Cheryl Guttman

The MK-2000 (Nidek) is an easy-to-use and easy-to-maintain automated microkeratome that LASIK surgeons can depend on to produce quality keratectomies with an almost negligible risk of complications, says a Mexican ophthalmologist.

Arturo S Chayet MD, Director, Codet Aris Vision Institute, Tijuana, Mexico has used the MK-2000 in approximately 7,000 eyes and in no case over the last 3,000 procedures, did he need to abort or postpone the surgery due to a microkeratome-related complication.
He said the MK-2000 has performed very reliably in producing flaps of varying sizes and thickness, even when making very thin flaps.

"Considering its safety and efficacy along with the ease of its one-handed operation and maintenance, the MK-2000 can be considered technician-, surgeon- and patient-friendly and an excellent microkeratome choice for high volume practices," Dr Chayet remarked.

He noted that he has never encountered problems with anterior chamber entry or loss of suction leading to the creation of an improper flap.
No eyes in his large series developed worse than 1+ diffuse lamellar keratitis. He did experience one free cap and one incomplete cap when using a prototype of the MK-2000 but neither of those events have been a feature of his experience when using the finished instrument.

Small epithelial abrasions have been noted in a handful of eyes (<0.5%), and particularly with use of the largest 9.5 mm ring.
However, a 2+ or worse abrasion occurred in only one case and that individual had an unrecognised basement membrane dystrophy.

Dr Chayet also conducted a study investigating the reproducibility of flap thickness using the MK-2000. In that trial, flap thickness (mean ± SD) using this microkeratome fitted with the 130-micron head was 115 ± 14 microns. Flaps cut with the 160 micron head measured 135 ± 22 microns.

"This data confirm that we can reliably achieve a very thin flap using the MK-2000 with its 130 micron blade. The standard deviation was somewhat higher using the thicker 160 micron head but it was still very acceptable," Dr Chayet explained.
He attributes the safety performance of the MK-2000 to several design features. The instrument has a unique suction ring that measures only 19 mm in diameter and has a low profile permitting placement in any type of eye or orbit.

Designed for eyes of any size
"Nidek, the Japanese manufacturer of the MK-2000, designed this device for use in Oriental eyes and it fits well into any small eye. With its small footprint, this microkeratome also allows the surgeon to do any type of tonometry to confirm the adequacy of suction before cutting is begun," Dr Chayet noted.

The suction ring also features dual suction so that IOP rises immediately and is sustained at over 100 mm Hg.
In addition, the construction of the MK-2000 prevents obstruction from lids and lashes. Jamming during cutting is not an issue because there are no gears, guides or external stoppers.

Independent motors control blade oscillation and advancement. There is no oscillation in reverse mode, so the risk of epithelial defects is minimised. The design also allows surgeons to visualise flap creation while it is occurring.
The MK-2000 only creates nasally hinged flaps which some specialists might consider a design limitation.

But Dr Chayet says there is more ablation area with a nasal-hinged flap because the cornea diameter is larger horizontally. That orientation has a safety advantage since it is associated with less dry eye than a flap with a superior hinge.

Three ring sizes available for use with the MK-2000 include 8.5 mm, 9.0 mm and 9.5 mm.
Dr Chayet has developed a nomogram for ring selection, choosing the largest ring for all hyperopic cases and the 9.0 mm ring for all bitoric ablations.
Corneal steepness is factored into the process of ring selection for myopia treatments. In such cases, he uses the smallest ring in eyes with steep corneas (K>42 D), the intermediate size for K ranges from 40 D to 42 D and the 9.5 mm ring in flatter eyes with K readings <40 D.

Dr Chayet added that the MK-2000 also has good acceptance among his operating room technicians who are responsible for microkeratome assembly and care. Since it has only five parts, the MK-2000 is easy to put together and easy to clean, he explained.

Dr Chayet is an international investigator for Nidek. He was among a group of leading surgeons who were asked to present their experiences with the different microkeratomes during a refractive surgery subspecialty meeting held in conjunction with the annual meeting of the American Academy of Ophthalmology.

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