October 2007

 

CATARACT/ IOL

 

Diamonds: steady appeal


by Rich Daly EyeWorld Contributing Editor

 

Diamond Knives-Cataract 1

Diamond Knives-Cataract 2

 

The extra sharpness provided by diamond knives also requires a careful surgical approach among new users.

Diamond knives offer a range of advantages in cataract surgery but surgeons trying them for the first time may face a learning curve. Ronald L. Fellman, M.D., associate clinical professor of ophthalmology, University of Texas Southwestern medical Center, Dallas, suggests that new users initially go slow with the forward movement to get the feel of the knife. Dr Fellman said he has relied on diamonds for many years to make his corneal incisions. He also relies on them to make the paracentesis.

Dr. Fellman prefers the diamond blades for his clear corneal incisions because they “create an effortless plane on a consistent basis and seem to require less force than the metal blades that are used in my surgery center.”

Elizabeth A. Davis, M.D., adjunct clinical assistant professor, University of Minnesota, agreed that surgeons new to diamonds may have a small learning curve since much less resistance is encountered when entering tissue.

”Diamond blades are still significantly sharper than any metal blade,” said Dr. Davis, director, Minnesota Eye Laser and Surgery Center. “Therefore, incisions can be much more precise in terms of size, length, and depth.”

Dr. Davis, who prefers diamond knives for cataract and phakic IOL surgery, also noted that the sharper blade allows better cutting and less shearing force applied to the tissue, which allows for improved sealing of the wound.

Surgeons new to diamonds might benefit from the use of a second instrument, such as a pair of toothed forceps to hold counter traction via the limbus or paracentesis can help control entry, Dr. Davis said.

Tips offered from experience

Dr. Davis prefers to use a tri-faceted diamond knife. The diamond knives she prefers for standard coaxial cataract surgery, the paracentesis and micro-incision coaxial cataract surgery are the E0170 Lindstrom etched diamond keratome (STORZ, Bausch & Lomb, San Dimas, Calif.) and the 3-D Diamond Blade (Rhein Medical Inc., Tampa, Fla.).

Robert H. Osher, M.D., professor of ophthalmology, University of Cincinnati, Ohio, is a self-described “fanatic of diamond” knives, who helped introduce them to ophthalmology. He uses diamond knives in the majority of his cases because they provide the perfectly square incision he uses with 2.2 micro-coaxial phaco with torsional ultrasound.

“These incisions are so competent and so good and that’s why in a nut shell microcoaxial with torsional ultrasound is growing so much,” Dr. Osher said.

He obtains his “very precise square incision” with a 2.2 mm diamond knife (Duckworth & Kent, Herdfordhire, England).

Dr. Osher’s standard surgical approach uses three diamonds for a three-plane incision. The first grooved diamond knife makes a groove, followed by a 1 mm tri-faceted diamond uphill dissection through clear cornea, and a third 2.2 mm diamond enters the chamber. This is followed by a 1 mm tri-faceted diamond stab incision for a side port. “Not everyone has to go to that length,” Dr. Osher said, about his surgical approach. “The incisions are such that I don’t ever see a wound leak, and that’s probably that why I’ve got the world’s lowest rate of endophthalmitis for over 30 years.”

Mark Packer, M.D., clinical associate professor, Casey Eye Institute, Oregon Health & Science University, Portland, Ore., uses diamond knives to make his 1.2 mm to 1.4 mm trapazoidal bimanual microincision cataract surgery incisions.

In addition, diamond knives have proven effective in performing consistent limbal relaxing incisions, especially in thick corneas, he said. Dr. Packer’s limbal relaxing technique includes the use of pachymetry, measurement of the 10 mm optical zone, and always cutting to 90 percent depth. The best results come from a continuously variable depth 600 micron blade (Elite II, Mastel Precision, Rapid City, S.D.), which comes with 360 degree plate surrounding the around the knife that guarantees a perpendicular cut guarded to the desired depth. “Using diamond blades that are precisely ground and continuously adjustable for limbal relaxing incisions is a real advantage over using metal blades that may or may not cut to the depth you want and cause tearing or stretching of tissue, which almost certainly ends up in an epithelial defect,” Dr. Packer said.

Surgeons offer a note of caution

New users to diamond knives also should note that their high cost necessitates careful handling. The blades require kid gloves by surgeons and staff during use and cleaning to prevent nicks and other damage to the blades.

Another area of caution is to ensure the long-used blades have a quality cleaning regimen to protect the instruments from the ravages of use and pathogens. Dr. Fellman noted that his office previously used an ultrasonic cleaner but that still allows potential contamination.

Many surgeons have developed a specific protocol on the handling and cleaning of their diamond knives, starting with the removal of debris from them immediately after use. An immediate rinse at the time of surgery with balanced salt solution (BSS), followed by a rinse with distilled water can prevent salt build up. Then wiping the knife off with a wet sponge and putting it through the sterilizer afterward. When debris is not easily removed, some surgeons direct staff to hold the extended blade in an ultrasonic bath, without letting the blade touch the metal ultrasound unit or the solution to come up to the workings of the blade handle.

Dr. Davis’ office has found an effective regimen in designating a technician to clean the diamond blades after each case, which includes rinsing them under running water with the blades not retracted and then flash cleaning them. Any remaining build up is removed from exposed blades placed in the ultrasonic cleaner for 3 to 5 minutes. “They are so fragile that anything else seems to damage them,” she said.

Although diamond blades require special cleaning that disposable blades do not, The benefits outweigh the costs when the blades are cared for appropriately, Dr. Davis said.

“A typical diamond can last for years, hence easily paying for itself,” she said.

Editors’ note: None of the surgeons reported financial relationships related to their comments.

Contact information

Davis: 952-885-2467, eadavis@mneye.com
Fellman: 214-360-0000, rfellman@aol.com
Osher: 513-984-5133, rhosher@cincinnatieye.com
Packer: 541-687-2110, mpacker@finemd.com

Diamonds: steady appeal Diamonds: steady appeal
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