Microkeratomes face off in study of blades, cut quality

Study assesses debris, blade edges and the resulting cut quality.

Issue: October 1, 2000

BOSTON - Scanning electron microscopy of microkeratome blades showed variable edge quality between samples, although the clinical impact of these differences remain to be studied, said R. Doyle Stulting, MD, PhD.

Researchers sent letters to the manufacturers of microkeratomes and blades and requested that they submit two blades, as well as globes cut with flaps.

Those included were the Krumeich-Barraquer Microkeratome (Summit Autonomous Inc., Waltham, Mass.), Innovatome (Innovative Optics, Albuquerque, N.M.), Precision Edge (Oasis Medical, Glendora, Calif.), Med-Logic's blade (Laguna Niguel, Calif.) for Bausch and Lomb's Hansatome unit, the FlapMaker (Medtronic Solan, Jacksonville, Fla.) and the Hansatome (Bausch & Lomb Surgical, Claremont, Calif.). All companies except Innovative Optics and Med-Logics sent globes. Moria SA (Antony, France) submitted their materials late and were not included.

Dr. Stulting and peers at Emory University in Atlanta examined the blades and their cuts and presented the study results at a microkeratome symposium conducted at the American Society of Cataract and Refractive Surgery meeting.

Study set-up

Blades arrived in their normal packaging material. An unbiased examiner opened the packages in a clean room and examined blades and packages under a dissecting microscope. Observers looked for stains, foreign bodies, surface irregularities and any other defects that they thought might be important to the blade users.

Observers then mounted the blades using talc-free gloves to examine them with a scanning electron microscope. No metals touched the blades at any time during the processing.

Observers used a standard photography process. The first photo was a 20-times magnification of the entire blade. The second series of pictures took three photographs at 200-times magnification across the blade - one in the center and two at each edge. Researchers then took four 1,000-times magnification pictures - two on the edge and two at the center.

The companies cut flaps on eye bank eyes with their microkeratomes and submitted the globes on ice. Observers fixed the selections in formalin and mounted each for scanning electron microscopy.

Researchers created a grading system of 1 to 4 based on selected photographs from the blades and the cut specimens. Observers had excellent agreement, and it made no difference which observer was looking at the blades or the specimens, Dr. Stulting said.

Variable qualities

Observers first made descriptive analyses of blades and packaging.

During the opening of the Krumeich-Barraquer outer package, observers saw packing fibers.

"While they were not present within the inner packaging, they did fragment, and there is no question that if care is not taken, these could easily spill over into the sterile field or into the packing area," Dr. Stulting said. "The packaging in the blade can certainly be responsible for flap complications, such as thick ones, thin ones, button holes, interface debris and intralamellar keratitis."

Observers noticed a modest amount of debris and small scratches on the blade. Edge quality varied between the two sample blades. The first received a rank of 1, and the second received a rank of 3.7. Observers ranked the bed quality from 2.8 to 3.7. The edges varied from vertical to sloped, and the edge chatter was present or absent depending upon the specimen that was examined.

"There was considerable variation in the quality of the cut that we examined in the three specimens that we saw," Dr. Stulting said.

Innovatome blades showed stains, some debris and moderate surface scratching. One blade edge was of good quality, and one was of rough quality, Dr. Stulting said. Bed quality varied from quite smooth to moderately rough. The edge angle varied, and in two of the three specimens, there was a significant amount of edge chatter. Observers ranked blade edge quality as 2.7 or 2, and bed quality ranged from 1.1 to 3.

The Oasis Precision blade samples were reasonably clean and free of debris and stains. Some machining marks existed, he said. Observers ranked blade edge as 3.2 and 3.3. The company did not send tissue samples.

The Med-Logics blade showed machining marks, but the blade was clean and without debris or stains, Dr. Stulting said. Blade edges were near the optimal grade of 3.6 and 3.7 in smoothness. The company did not send samples of cut blades.

Microscopy of the FlapMaker blades showed a large stain, and observers found it had an edge quality of 4. The blades had no debris, a small number of stains and the most consistent edge.

However, the blades left a rough bed quality, Dr. Stulting said. Observers ranked the bed quality between 1.7 and 2.1. "Edge angle is vertical sloped and vertical for the three specimens, and blade chatter was present in all of the specimens."

Bausch & Lomb's Hansatome had a small amount of debris on the blade, no stains and a smooth cutting edge ranked at 3.9 and 4. The bed quality was ranked at 1.8 and 2.

More study needed

"We found considerable variability in packaging, blade edge and flap characteristics among the manufacturers," Dr. Stulting said. "The clinical relevance of what we observed here is certainly yet to be determined. Whether manufacturing differences in the edge of the blade are the most significant things that we should be paying attention to clinically is not established. But, it does give us some ideas about the consistency of the manufacturers, I think, and the care in which blades are created."

Also, the study used a limited number of specimens that may not completely represent the blade lots made over a long period of time. Globe samples may have had post-mortem artifacts that may have caused some of the variability seen in the edge configuration and bed smoothness.

"Certainly, more study and clinical correlation are needed, and we need a laboratory model to help us evaluate these characteristics of microkeratomes more effectively," he said.

Arrows point to debris and scratches at 200X magnification on the SKBM. COURTESY OF R. DOYLE STULTING, MD.	At 1,000X magnification, the SKBM blade edge shows variable quality. COURTESY OF R. DOYLE STULTING, MD.
Arrows point to stains, debris and moderate scratching on the Innovatome blade. COURTESY OF R. DOYLE STULTING, MD.	Significant edge chatter shows up on the Innovatome. COURTESY OF R. DOYLE STULTING, MD.
A 100X magnified view shows a reasonably clean Oasis Precision Edge blade. COURTESY OF R. DOYLE STULTING, MD.	A 200X magnification shows the Med-Logics blade to be clean with a near optimal edge. COURTESY OF R. DOYLE STULTING, MD.
A stain shows up at 200X magnification on the Flapmaker blade.	Best edge quality shows up on the Flapmaker blade at 1,000X magnification.
The Bausch and Lomb Hansatome at 200X magnification shows good edge quality with some debris.	The Bausch and Lomb Hansatome shows vertical slope and chatter.

Summary: blade edge quality

Summary: flap bed smoothness

For Your Information:

R. Doyle Stulting, MD, PhD, can be reached at 875 Johnson Ferry Road, Atlanta, GA 30342; (404) 250-9700; fax: (404) 250-9006. Dr. Stulting has no direct financial interest in any product mentioned in this article, nor is he a paid consultant for any companies mentioned.

Bausch & Lomb Surgical can be reached at 555 W. Arrow Highway, Claremont, CA 91711; (909) 624-2020; fax: (909) 399-1422.

IInnovative Optics can be reached at 6808 Academy Parkway East, NE, Building C, Suite 1, Albuquerque, NM 87109; (505) 341-2577; fax: (505) 341-2575.

Med-Logics can be reached at 30251 Golden Lantern E-207, Laguna Niguel, CA 92677; (949) 588-7287; fax: (949) 588-7267.

Medtronic Solan Ophthalmic Products can be reached at 6743 Southpoint Dr. N, Jacksonville, FL 32216-0980; (904) 279-7552; fax (904) 279-2630.

Oasis Medical can be reached at PO Box 1137, Glendora, CA 91740; (626) 914-2891; fax (626) 914-2285.

Summit Autonomous Inc. can be reached at 21 Hickory Drive, Waltham, MA 02451; (781) 890-1234; fax: (781) 890-0313.