Today, minimizing postoperative astigmatism has become the standard of care for refractive surgery, especially when a patient is receiving a high-tech implant that requires vision with as few aberrations as possible. Hand-made limbal relaxing incisions have been a time-honored way to accomplish this. Today, surgeons’ options for addressing astigmatism have grown. Nevertheless, LRIs haven’t gone away.
R. Bruce Wallace III, MD, FACS, founder and medical director of Wallace Eye Surgery in Alexandria, Louisiana, and clinical professor of ophthalmology at Louisiana State University and Tulane Schools of Medicine in New Orleans, has been making limbal relaxing incisions for years. “Given all of today’s new intraocular lens technology and new surgical options and techniques, patients expect to have extraordinary postoperative vision,” he says. “Giving them that requires addressing corneal astigmatism.
“Using manual limbal relaxing incisions to reshape the corneal surface is a tried-and-true method for addressing astigmatism intraoperatively or postoperatively, especially when it’s a small amount of astigmatism,” he continues. “It’s a great way to help patients achieve excellent postoperative vision, which is even more important when premium IOLs are involved. And today, the tools for creating manual LRIs continue to evolve, whether you prefer diamond knives or disposable blades.”
Dr. Wallace notes that with so much other new technology available—e.g., femtosecond lasers and toric intraocular lenses—the relative importance of LRI knives depends on the individual surgeon’s preferences and the patient’s circumstances. “For example,” he says, “making limbal relaxing incisions with a femtosecond laser generally isn’t a good option for a postoperative touchup, unless the surgeon doesn’t do manual LRIs at all. Typically, femtosecond laser LRIs are only made during cataract surgery.
“Usually this achieves the desired refractive result, but occasionally a touchup may be needed,” he continues. “If that’s the case, using the laser postoperatively would be relatively expensive, and I don’t think it offers much more predictability than a manual LRI. Why take the patient back to the OR and pay the fees to use the laser when you can just correct the problem by creating an LRI manually in the office?”
Toric IOLs have also become an increasingly popular way to address astigmatism, but Dr. Wallace points out that manual LRIs have one significant advantage over toric IOLs. “An LRI can be quite effective for correcting low levels of astigmatism,” he says. “If a patient only has 1 D or 1.5 D of cylinder, a toric IOL might be overkill. An LRI can easily correct that amount of astigmatism, and it’s much less expensive. The only real requirement is that the surgeon be comfortable performing the incision.”
Dr. Wallace has created three short instructional videos explaining how to create manual limbal relaxing incisions, which can be viewed on YouTube. Part one is available at youtube.com/watch?v=SgM-Ud_6lYI. (You can also find the videos by going to YouTube.com and searching for “Wallace LRI.”)
An LRI Knife Sampler
Here’s a brief list of some of the LRI knives and kits that are currently available:
• Koch Double-footplate LRI Diamond Knife. This knife uses a tri-facet blade for a controlled entry and a double-footplate for the creation of consistent wound architecture, according to the company. It has side-cutting edges for easy extension of the wound. It comes in three depth settings: 500; 550; and 600 µm. (Also available with 450-, 500-, and 550-µm depth settings for small pupils.)
• Zaldivar LRI Diamond Knife. This uses a tri-facet blade for controlled entry and side-cutting edges for extending the wound. ASICO says the single footplate allows for better visualization. It has a preset depth setting of 600 µm.
• Fukuyama LRI Diamond Knife. This lancet blade also has side-cutting edges for easy wound extension and a double footplate. Precise depth settings go up to 2,000 µm.
• Multi-incision Diamond Knife. This is a 10-facet blade with side-cutting edges and a single footplate for better visualization. Seven adjustable depth settings up to 6,000 µm for various procedures, with three depth settings specifically for performing LRIs: 500; 550; and 600 µm.
• Three-step LRI Diamond Knife. The three-step has a trifacet blade for controlled entry and a single footplate. It has side-cutting edges for easy wound extension, and three depth settings: 500; 550; and 600 µm. (Also available with 450-, 500-, and 550-µm depth settings for small pupils.)
• Dual Micrometer LRI Diamond Knife. This six-facet blade also has side-cutting edges for easy wound extension and a single-footplate. Its depth settings go up to 2,000 µm.
• Gemcision 550-µm Angled LRI Knife. This particular knife is also available in 300- and 600-µm depths.
Storz (Bausch + Lomb)
• Wallace LRI Diamond Knife Kit. The kit includes an LRI diamond knife (600 µm preset blade depth). The knife has a straight, 120-mm retractable handle and a 0.2-mm front flat tip. The company says the single footplate allows easier visibility of the knife as it passes through corneal tissue. The knife’s handle is designed for finger twirling as the blade follows the arcuate pattern of the limbus. It comes with a sterilizing tray. (Also available through Ambler Surgical.)
• Donnenfeld LRI Diamond Knife. This uses a single-footplate design, and has a fixed, 0.6-mm depth. The tri-facet 20-degree blade is for incisions to the left or right and is angulated 10 degrees for better alignment and approach. The shorter handle length promotes ease of use under the microscope or at the slit lamp, the company says. The blade assembly retracts into the handle for safe storage. (Also available from Duckworth & Kent and MSI Precision Specialty Instruments.)
• Nichamin LRI Diamond Knife. This knife’s small footplate is curved to conform to the fixation/degree gauge; it provides a guide for making the arcuate incision at the limbus. The company says that the fine 15-degree, 100-µm diamond blade with a micro-flat tip ensures blade stability and a “smooth glide” through corneal tissue. Step adjustment allows surgeons to dial in the desired incision depth, ranging from 0.5 mm to 0.8 mm in 0.05-mm increments. (Also available from MSI Precision Specialty Instruments.)
• Oyakawa LRI Diamond Knife. The company says this tri-facet, 20-degree blade offers a very thin profile for tracking through the cornea and a small square tip configured for accurate depth control. The footplate is designed to ease the movement of the blade through the LRI incisions and allow for visualization when aligning the blade to the desired incision width. The micrometer handle allows depth adjustments in 0.01-mm steps. The blade is retractable.
• AccuSharp Guarded Ophthalmic LRI Knife. MST describes these knives as disposable, single-use metal blades with “superior sharpness.” The knife’s handle features smooth, single-handed blade retraction and ergonomic design. The blades are 1 mm wide, available in 500-, 550- and 600-µm preset incision depths. The knives come sterile, packaged individually, with six knives per box.
• LRI Step Knife. Katena says this is a gem-quality diamond knife with a titanium handle, a six-facet blade for bi-directional cutting and three precalibrated depth settings of 500, 550 and 600 µm. A single, highly polished footplate provides a smooth gliding surface and serves as a depth guard while permitting full visualization of the blade. The company says it’s available in single, double, triple and micrometer settings.
• Seven different LRI knife options are available: 20-degree Tri-facet; Brown Universal Cataract Knife; 45-degree double edge; lance; standard tri-facet; Stat III; and Woody Davis Triple 90.
• Five LRI Knife options are available. All models feature 20-degree tri-facet blades and titanium handles. One features three preset depth settings of 500, 550, and 600 µm. Other models feature preset depths of 500 or 600 µm; some are designed for use at the slit lamp.
• Limbal Relaxing Incision Kit. This is a single-use kit with a disposable 600-µm knife. The knife creates precise-depth incisions with a pre-set guard, the company says, and the bi-directional blade cuts left or right. Multiple depth options are available. The LRI kit includes a surgical marking pen and 13-mm swivel fixation ring, with guide marks at 10-degree increments.
MSI Precision Instruments
• LRI Knife Micrometer. This is a single footplate, ultra-thin knife:
1 mm wide and 0.1 mm thick with a 60-degree truncated lance. The blade cuts in both directions. The micrometer is in 0.1-mm increments ranging from 0 to 1.5 mm.
• Precision Aluminum Silver and Blue Economy Trifacet Diamond Knife. This knife is 1 mm wide and 4 mm long.
• Precision CV Universal Diamond Knife. This knife has a titanium J-slot bayonet handle design with a single footplate. The knife is preset at 0.5 mm. The 20-degree, 0.4 truncated lance is 1 mm wide and 0.1 mm thick. It’s also available with three settings: 0.5; 0.55; and 0.6 mm.
• Multiple LRI knives are available. The company says these are affordable knives with different blade and tip characteristics; they offer diamond and sapphire knives. REVIEW