Hitting the Clinic with the KDB

When to use the dual blade

Nathan Radcliffe: “If you have experience with trabecular bypass, or other types of incisional trabecular meshwork (TM) surgeries, you want to approach the Kahook Dual Blade (KDB) with an open mind. In my experience, the dual blade has delivered unsurpassed efficacy in terms of lowering IOP, which I couldn’t have predicted based on my experiences with other types of trabecular bypass.” Leonard Seibold: “The KDB has allowed me to perform a more complete goniotomy than other methods available, and a more complete TM removal, in a simple yet elegant manner. But you should have a good foundation in intraoperative gonioscopy in order to perform this surgery to the best of its capabilities.”

Selecting the right patient

NR: “The KDB procedure is versatile – it can be performed in patients combined with cataract surgery, and also in phakic patients with 20/20 vision. It can also be used in patients who are already pseudophakic, and alongside other procedures, such as other types of trabecular bypass (if one wants to expand the number of accessed collector channels), glaucoma drainage devices, endocyclophotocoagulation, and more.” LS: “Any patient with open angle glaucoma, whether primary or in some cases secondary, can be a candidate. The most profound pressure reductions I’ve found are in patients who have pigmentary or pseudoexfoliative glaucoma – where we know the site of obstruction is at the level of the TM, so by removing that tissue you can dramatically increase aqueous outflow and lower IOP. Additionally, any patient with uncontrolled IOP despite medications, or who is intolerant, allergic, or not adhering to their medications, could potentially benefit.”

Getting the preparation right

NR: “Using gonioscopic visualization, you want to make sure that you have adequately inflated the anterior chamber, as this is going to be important during the TM treatment. You want the eye to be slightly pressurized, certainly higher than episcleral venous pressure, but not so high that you’ll collapse the TM. A pressure of around 20 mmHg is ideal.” LS: “Like in any angle surgery, a good view of your target tissue is key – in this case that’s the TM. Examine these patients closely in your preop evaluation, because when you’re deciding who’s a candidate you want to be able to visualize good angle anatomy and landmarks, so you know you’ll be able to see the target tissue well in surgery.”

Top technique tips

NR: “You have several choices for how to make the parallel incisions in the TM, but these days I start straight nasally, so either the 3 o’clock or 9 o’clock position, and I do two passes. The first is a forehand pass, so if I’m operating on the right eye, I make a temporal incision, and I’ll treat from the 3 o’clock position up to about 1 o’clock, as far superiorly as I can. I make sure that I’m seeing the bare posterior wall of the canal of Schlemm. Then, I don’t bring the KDB out of the eye, but simply reverse its direction and treat from the 3 o’clock position down to 5 o’clock or lower. When the dual blade procedure is performed with cataract surgery and TriMoxi is given intravitreally, excellent outcomes can be achieved, without the need for any postoperative pressure lowering or anti-inflammatory drops – which patients really appreciate.” LS: “You want to avoid pushing outward too much on the eye – if you see the eye rotate as you move the blade, you’re pushing too far, and could potentially damage the back wall of the canal of Schlemm. If you’re not pushing enough or you’re not well seated within the canal, you’ll only be superficially scraping the TM, and you won’t get the full benefit of what the blade can do. You should ensure the blade is seated well within the canal so that it glides smoothly as you advance it.”

IOP lowering and medication reduction: what to expect

NR: “Trabecular bypass has a reputation for being relatively safe, but lacking efficacy. With the KDB, we are seeing postoperative IOPs in the low teens, and getting 5–6 mmHg of pressure reduction, depending on whether cataract surgery was also performed.” LS: “Reviewing our KDB cases combined with cataract surgery, we are achieving IOP reductions of around 30 to 35 percent, in addition to eliminating one topical medication. In some cases, I’ve been able to take patients on three medications and uncontrolled IOP down to a controlled pressure without medication. Decreasing the number of eyedrops a patient has to take reduces the worry, hassle and cost associated with chronic topical therapy. It can truly have a profound effect on their quality of life.”