Refractive Surgery
Disposable blade dominance grows

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Surgeons cite increasing use of metal blades for a variety of ophthalmic procedures, including ones previously performed with diamond knives

As metal blades become increasingly sharp and precise surgeons are finding them more reliable for use in an increasing number of procedures where they previously used diamond knives.
Terry Kim, M.D., associate professor of ophthalmology, Duke University School of Medicine, Durham, N.C., said improvements in disposable blades have led him to rely on them exclusively.
“The design of disposable knives has improved considerably over the years, and I can’t think of any patient or complication scenario that would preclude the use of a disposable knife in cataract surgery,” Dr. Kim said.
Dr. Kim uses ClearCut Slitknives (Alcon, Fort Worth, Texas) for cataract surgery, including a 2.2 mm ClearCut Single-Bevel knife for his main clear corneal incisions and the 1.0 mm ClearCut Dual-Bevel Sideport knife for his paracentesis incisions. He also uses disposable blades for limbal relaxing incisions. “Overall, I have been very impressed with the sharpness, precision, and the consistent performance of these disposable blades,” Dr. Kim said. An additional benefit from the use of disposable blades, Dr. Kim said, is their potential to decrease the risk for toxic anterior segment syndrome.
Francis S. Mah, M.D., co-medical director, Charles T. Campbell Ophthalmic Microbiology Laboratory, University of Pittsburgh School of Medicine, Pittsburgh, has come to reply on disposable blades for routine cataract procedures, Descemet’s stripping endotheilial keratoplasty, and corneal transplants, although he continues to use diamond blades for LRIs.
Metal blades are easier to use, Dr. Mah said, because their relative dullness makes them safer, whereas the sharpness of diamond blades requires the use of pearl-driven techniques. The differences can make it difficult for surgeons to transition between disposable and diamond blades.
Dr, Mah notes that incremental improvements over recent years have resulted in disposable blades that are “much, much sharper” than their predecessors.
Eric D. Donnenfeld, M.D., co-chairman, Cornea, Nassau University Medical Center, East Meadow, N.Y., also has come to rely on newer generations of disposable blades from Becton, Dickinson and Co. (B&D Ophthalmic, Franklin Lakes, N.J.).
“They make the internal diameters greater than the external diameters, which is great so they don’t oarlock,” Dr. Donnenfeld said about the disposable blades he uses in cataract surgery.

Precautions needed

Although disposable blades lack some of the disadvantages of diamond blades, including the potential for long-term damage, higher cost and maintenance concerns, surgeons need to look for unusual dullness in disposable blades, Dr. Kim said. That wariness should extend to intra-operative assessments of the blade’s sharpness “Not infrequently and unbeknownst to the surgeon, the tips of these disposable blades can be easily dulled or damaged during removal from packaging, hitting the instrument tray, etc.,” he said. “As a result, you may encounter unusual resistance at the start of or during wound construction.”
In such instances, both Drs. Kim and Mah warn against forcefully pushing the blade to initiate or continue the incision, which can result in an irregular incision or damage to the cornea and anterior capsule. Instead, use a new disposable blade to complete the incision.
“A lot of times you’ll see a resident just keep pushing and the end up pushing too far and nick the capsule or something worse,” Dr, Mah said.
Another potential problem with disposable blades, Dr. Mah noted, is the possibility of small but significant variations in size. The issue is even more important in moving to smaller incisions, such as his transition from 2.75 mm incision phacoemulsification to 2.2 mm incisions. He has discovered that small variations in blade sizes among some manufacturers can result in wounds that are smaller than 2.2 mm, which can disallow sufficient infusion into the eye. “A 2.2 mm blade may not be 2.2 mm,” Dr. Mah said. He suggested that surgeons ask manufacturers and sales companies for information on the standard deviations they allow in their blades. Another way to avoid such variations is to use equipment that manufacturers have designed to accompany specific phacoemulsification systems. Dr. Mah uses disposable blades matched to the Intrepid micro-coaxial system (Alcon).
Another option is to use a corneal measuring instrument, or “dipstick,” after the incision is made to check its size. However, make sure such equipment is ready at the time of surgery to avoid wound burns or shallow chambers, he said.
A recent concern that has arisen in the use of disposable blades is the consideration of plans by state and federal regulators to prohibit the re-use of disposable blades, which would “significantly increase the cost of surgery,” Dr. Donnenfeld said.
The change would significantly affect many areas of ophthalmic surgery because some disposable knives are fully functional for up to 20 procedures, he said.

Not all created the same

The use of disposable blades also is likely to be impacted by emerging research that compares their relative effectiveness. Research Dr. Kim co-authored was published in the Journal of Cataract and Refractive Surgery in 2009 that compared the effects of silicone blades to steel blades on corneal wound integrity and architecture as part of an eyebank study.¹ The study found less gross wound leakage and less tissue disruption under scanning electron microscopy among the clear corneal incisions created by silicone blades compared to those created by metallic blades.
“Based on these results, further study is certainly warranted to determine the clinical relevance of these experimental findings,” Dr. Kim said.

¹ Etter J, Berdahl JP, Jun BK, Caldwell M, Kim T. Corneal Wound Integrity and Architecture After Phacoemulsifcation: Comparative Analysis of Corneal Wounds Created by Silicone and Steel Blades. J Cataract Refract Surg 2009; 35(7): 1313-1314.

Editors’ note: Dr. Kim has financial interests with Alcon (Fort Worth, Texas). Dr. Donnenfeld has financial interests with Abbott Medical Optics (Santa Ana, Calif.) and Allergan (Irvine, Calif.). Dr. Mah has no financial interests related to his comments.

Contact information

Donnenfeld: 516-766-2519, eddoph@aol.com
Kim: 919-681-3568, terry.kim@duke.edu
Mah: 412-647-2214, mahfs@upmc.edu