In this video, Leo Seibold, MD, offers an overview of the key design features of the Kahook Dual Blade (KDB), pearls for success with KDB, and an introduction to the latest version of the device, the KDB Glide (New World Medical).
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Overview of the KDB Glide
Since its Food and Drug Administration (FDA) approval and US commercial launch in 2015, the Kahook Dual Blade—named for its inventor, Malik Y. Kahook, MD—has offered surgeons a well-tolerated approach to reducing intraocular pressure in glaucoma patients coupled with a favorable safety profile.
One of its biggest proponents is glaucoma specialist and cataract surgeon Leo Seibold, MD, from the University of Colorado. In this session from the Interventional Mindset, he explains why and offers surgical pearls for patient selection, which might enhance outcomes when using this device.
KDB design
KDB was designed to not only incise trabecular meshwork, but to perform an excisional goniotomy. By excising a large piece of the trabecular meshwork, as opposed to just cutting through the tissue, the surgeon can create a much larger cleft in the trabecular meshwork, allowing easier access for aqueous to potentially outflow through the pathway in the long-term on a continuous basis.
Removing more tissue upfront decreases the chance of the opening becoming walled off or significantly narrowed through the scarring process. In turn, there is an increased chance of reaching the sought-out target pressure and possibly reducing the number of glaucoma medications taken by the patient.
Indications for KDB
KDB is indicated for the treatment of open-angle glaucoma (OAG) and ocular hypertension. Ideal patients include individuals with uncontrolled intraocular pressure (IOP) as well as patients who struggle with controlling IOP due to non-compliance issues or topical ophthalmic medication intolerance.
It is approved as both a standalone procedure and for use in conjunction with phacoemulsification (phaco) cataract surgery on eligible patients.1
Two key features of the KDB are the sharp tip and the ramp. The sharp tip is fabricated to pierce easily through the trabecular meshwork, while the ramp facilitates the lift and stretch of the tissue. Combined with the dual-blade, this allows the surgeon to easily create two precise parallel incisions and a clean excision of the strip of TM.
Versatility of the KDB
Dr. Seibold’s favorite aspect of the KDB is its extreme versatility. As a stand-alone microinvasive glaucoma surgery (MIGS), the device can be used in patients with all levels of glaucoma—mild, moderate, and advanced—including pediatric patients. It also can be highly effective as a combination surgery in patients who have both cataracts and elevated IOP but can also be performed on patients who are already pseudophakic.
Additionally, current literature continues to provide a growing body of evidence that demonstrates the KDB’s efficacy for patients beyond those with open-angle glaucoma. The surgery is also in reducing pressure and minimizing the medication burden for advanced glaucoma patients with chronic angle closure as well as those with uveitic glaucoma.
KDB’s ease of use
According to Dr. Seibold, the KDB procedure is relatively easy to add to your surgical armamentarium, as it leaves no implant behind and only requires the single-use blade along with a direct gonioscopy lens. This makes it an ideal entry point for ophthalmologists who are new to intra-operative gonioscopy or just entering the MIGS space. For these clinicians, he suggests utilizing model eyes in a wet lab.
The SimulEYE KDB/TrabEx/TMH provides a means to visualize and remove a realistic trabecular meshwork, which is invaluable in identifying the angle, achieving familiarity with the blade, getting comfortable in your hand position, and gaining the direct gonioscopic view.
Dr. Seibold introduces three different techniques
There are three primary techniques for utilizing the KDB: the inside-out, outside-in, and mark-and-meet. All three techniques allow for the creation of an easily removable, free-floating flap of trabecular meshwork tissue. Therefore, it is merely a matter of personal preference and discovering through practice which works best for your hands and your patient population.
Inside-out
With this technique, start with a forehand pass—from right to left—opposite the wound. Next, reverse the blade and, starting from your initial point of entry, cut in the opposite direction with a backhand motion, which allows you to treat the widest degree of angle. This applies to right-hand surgeons, with left-handed clinicians adjusting accordingly.
Outside-in
As implied in the name, the outside-in version is simply the antipode of inside-out. Start to the far right of your view and, using a forehand motion, slice towards the middle. Reverse the blade and, in a backhand motion, make an incision from left to right.
Mark-and-meet
The mark-and-meet method is perhaps the most popular and easiest to execute, as both motions are completed in a forehand manner. To perform the mark-and-meet technique, start at the far left of your view and make a small goniotomy incision. Next, go to the far right of your view and, keeping the blade in a forehand motion, cut from right to left until meeting with the initial incision.
Top five KDB procedure pearls
- Visualization is the key to success, hence, it is imperative to achieve a good view. To ensure an adequate view, inflate the eye with a cohesive viscoelastic so as not to have to contend with stria from the gonio lens sitting on an underinflated eye. This should keep the iris out of view and out of the way as well.
- Instead of working at a distance with a wider field of view, zoom in. Zooming in can aid tremendously in delineating where the targeted tissues lie.
- Employ trypan blue dye. If the angle is lightly pigmented, making it difficult to determine the borders of the trabecular meshwork, inject trypan blue at the beginning of the case to stain the TM. If performing KDB in combination with cataract surgery, allowing blood to reflex into the canal post-phaco can help better visualize the canal.
- Make certain both the patient's head and scope are tilted appropriately to attain an en face view. In the case of trabecular meshwork, it is essential to look straight on to best engage the blades and render the cleanest excisional goniotomy.
- Use the proper pressure. Initially, it takes an amount of outward force on the trabecular meshwork. With the blade slightly tilted, allow the tip to pierce through the trabecular meshwork and seat into the canal. Once this has occurred, flatten out the blade and glide in the canal. Dr. Seibold likens it to a hot knife through butter, when done correctly.
If the eye rotates as you're moving the blade, it indicates too much pressure is being applied. In this instance, relax pressure until you can advance the blade into the canal without any eye movement. In contrast, if a significant amount of the ramp or tip of the blade is visible, it implies you are not seated deeply enough.
To remedy, seat the footplate slightly deeper within the canal until the majority of the ramp is covered by trabecular meshwork. This allows the dual blades to get an excision of tissue as opposed to an undesirable single incision.
Introduction to the KDB Glide
Dr. Seibold credits Dr. Kahook and New World Medical for finding ways to improve on an already ingenious device. The KDB Glide boasts a significant design enhancement—both the side rails of the footplate and the plate itself are tapered, which permits it to more easily fit in the Schlemm’s canal as well as seat into a broader variety of canals.
The tapering allows the blade to glide into the canal and advance with minimal resistance; this is especially important in older patients whose anatomy tends to be narrower.
In closing
For surgeons just entering the realm of MIGS, the KBD Glide is an excellent device to incorporate into their glaucoma management strategy.
The insight and surgical pearls from this article can serve as a guide to help clinicians find the technique that works best for them and gain the confidence to introduce this valuable treatment to eligible patients.
Disclaimer: KDB Glide from New World Medical is indicated as a standalone procedure or in combination with cataract surgery for mild, moderate, or severe glaucoma. The medical opinions and views expressed in this article are those of Leonard Seibold, MD.
