Over time, use of minimally invasive glaucoma surgery (MIGS) in combination with cataract surgery has become commonplace in our clinic. With many effective options available, we always choose the procedure we believe will result in the best outcome, optimizing safety, long-term patient comfort, quality of life, and pressure control. The decision to perform any surgery for glaucoma is undertaken with great thought and consideration, weighing the benefits against the risks associated with incisional surgery. Thus, when we began to couple MIGS with cataract surgery, we necessarily scrutinized the role of MIGS procedures. We found that performing a MIGS procedure at the same time as cataract surgery added only a relatively small amount of additional risk.

Evolution of Combined MIGS-Cataract Options

iStent (Glaukos), approved only for use during cataract surgery, was among the first approved devices to create pathways from the anterior chamber through the trabecular meshwork. More recently, the Hydrus (Ivantis) implant was approved. Over time, the list of cataract-concurrent MIGS procedure options grew. Among them, excisional goniotomy with the Kahook Dual Blade (KDB; New World Medical) allowed for removal of a small strip of trabecular meshwork tissue to permit better aqueous access directly to Schlemm’s canal.

Cataracts are a condition every glaucoma patient will face eventually. It makes sense to explore techniques that, when cataract surgery is appropriate, allow both issues to be addressed at the same time. Although some MIGS procedures are available for use as standalone procedures as well as during cataract surgery, the accelerated acceptance of MIGS occurred in the context of cataract surgery. For example, I frequently see new patients in their 50s and 60s with glaucoma who have had no eye surgeries. At that time, they often have mild cataracts, and neither their glaucoma nor their cataracts require incisional surgery. Typically, it is prudent to first treat their glaucoma with medications and possibly in-office laser treatments, such as selective laser trabeculoplasty. When the cataracts mature, it then makes sense for us to consider a minimally invasive procedure in combination with cataract surgery, given that the risks associated with surgery are justified because the cataracts are impairing vision. Often, medication use can be reduced following the combined procedure.

Selecting the Best Option for Each Patient

The range of MIGS options continues to change. As new technologies emerge, we continue to modify the conversation about when to perform glaucoma surgery, with or without cataracts. Newer-generation MIGS procedures, traditional trabeculectomy, and tube shunt surgery all will remain options in the foreseeable future.

We began using the KDB for goniotomy in our practice a few years ago because we thought it could be a beneficial choice for patients with mild to moderate glaucoma. We have performed goniotomy surgery for many years but on a limited basis in certain patients. Goniotomy is commonly used as a first-line treatment for primary congenital glaucoma in children.¹ In such eyes, the angle tissue is typically under considerable tension, and with a straight single incision it stretches open spontaneously. This dynamic is not typically seen in older patients, and as such, a trabeculodialysis procedure is required, which is technically more demanding. When the KDB became commercially available in 2016, we were able to perform this procedure more elegantly. The difference is that the KDB is designed to excise and remove a strip of the trabecular meshwork rather than just incise it.² This fact has elevated goniotomy to the realm of MIGS procedures, and its use in adults has grown. Studies have shown that KDB goniotomy performed with cataract surgery significantly lowers intraocular pressure (IOP) without significantly affecting visual acuity.^3,4 In fact, it reduces IOP and medication use after surgery as or more effectively than iStent.^5,6 Further, unlike most MIGS procedures, goniotomy does not leave any hardware behind. Furhtermore, data suggest that goniotomy may provide better drainage than single-location stents because it collects aqueous from a wider area.⁷ These advantages have made goniotomy a more common surgery for this cohort of our glaucoma patients. In addition, a recent study comparing goniotomy to a single-location stent found that the KDB goniotomy vs iStent implantation had less impact on endothelial cell counts when combined with cataract surgery.⁸ Performing goniotomy with KDB compares well to other MIGS combination procedures without adding excessive operating room time.

Currently, I choose the KDB for more than 95% of my cataract patients with appropriate glaucoma diagnoses. In the other 5% of cases, the glaucoma is more advanced, and I am typically concerned that the patient’s optic nerve may not be resilient enough to handle a possible early, significant postoperative pressure spike. If I am not concerned about a spike, but I believe the goniotomy may not do enough, it is sometimes worth trying the KDB first and then performing another non-MIGS procedure if the IOP remains too high.

Cost, Codes, and Reimbursement

Coding for current MIGS options is typically straightforward, although insurance coverage may vary depending on the policy. iStent, iStent Inject, and Hydrus use a temporary Category III CPT code (0191T), as does Xen (Allergan) via an ab interno approach (0449T). Facility reimbursement for these codes has been established at the national level by CMS, while local Medical Administrative Contractors have set the physician fees based on local coverage decisions. As utilization increases, and more data are collected, the codes will likely become permanent Category I codes. In the meantime, however, there can be inherent challenges to reimbursement for procedures that use Category III codes, which can disrupt workflow and require extra staff time.

Because goniotomy is a well-established procedure, it has an established Category I code (65820). This code also covers the KDB. There is peace of mind in using a Category I CPT code, for which physician and facility fee payments are as well established as traditional cataract surgery. Reimbursements for temporary Category III CPT codes can vary and require additional hurdles, which can disrupt a practice.

Margins can also be greater for KDB compared to other options, according to our practice’s costs and reimbursements. Consider these 2020 numbers for KDB:

• The payment amounts for 65820 are $801.55 for the physician, $3,817.90 for the hospital, and $1,835.84 for the ambulatory surgery center (ASC);
• When we combine cataract surgery with goniotomy in an ASC setting, a multiple procedure reduction applies such that the CMS physician fee is $1,080.34 (100% x $801.55 + 50% x $557.58), and the ASC facility fee is $2,342.20 (100% x $1,835.84 + 50% x $1,012.72);
• Using the KDB during cataract surgery contributes to an ASC take-home margin of $2,342.20 - $495 cost of blade = $1,847.20 (minus the cost of any additional disposables); and
• Using the KDB for goniotomy as a standalone contributes to an ASC take-home margin of $1,835.84 - $495 cost of blade = $1,340.84 (minus the cost of additional disposables).

Looking to the Future

Goniotomy combined with cataract surgery provides a favorable risk-to-benefit ratio for appropriate patients, while at the same time helping to support the ASC financially. Looking to the future, procedure efficacy and safety are of paramount importance. However, given the challenging economics of medical practice, it is always nice when not only the patient but also the ASC benefits. GP

Andrew G. Iwach, MD, is executive director of the Glaucoma Center of San Francisco, associate clinical professor of ophthalmology at the University of California at San Francisco, and a faculty instructor at the California Pacific Medical Center Department of Ophthalmology in San Francisco, California. He is also active on the Glaucoma Research Foundation Board. Dr. Iwach reports consultancy to and speakers bureau membership with Bausch + Lomb and New World Medical, consultancy to Ivantis, and committee membership with Ophthalmic Mutual Insurance Company.

References

1. Drivas E, Panarelli J. Characteristics and management of primary congenital glaucoma. EyeNet Magazine. 2018.7:35-36.
2. New World Medical. Kahook Dual Blade instructions for use.
3. Hirabayashi MT, King JT, Lee D, An JA. Outcome of phacoemulsification combined with excisional goniotomy using the Kahook Dual Blade in severe glaucoma patients at 6 months. Clin Ophthalmol. 2019;13:715-721.
4. Dorairaj S, Tam MD, Balasubramani GK. Twelve-month outcomes of excisional goniotomy using the Kahook Dual Blade in eyes with angle-closure glaucoma. Clin Ophthalmol. 2019;13:1779-1785.
5. Lee D, King J, Thomsen S, Hirabayashi M, An J. Comparison of surgical outcomes between excisional goniotomy using the Kahook Dual Blade and iStent Trabecular Micro-Bypass Stent in combination with phacoemulsification. Clin Ophthalmol. 2019;13:2097-2102.
6. Le C, Kazaryan S, Hubbell M, Zurakowski D, Ayyala RS. Surgical outcomes of phacoemulsification followed by iStent implantation versus goniotomy with the Kahook Dual Blade in patients with mild primary open-angle glaucoma with a minimum of 12-month follow-up. J Glaucoma. 2019;28(5):411-414.
7. ElMallah MK, Seibold LK, Kahook MY, Williamson BK, Singh IP, Dorairaj SK; KDB Goniotomy Study Group. 12-month retrospective comparison of Kahook Dual Blade excisional goniotomy with iStent Trabecular Bypass Device implantation in glaucomatous eyes at the time of cataract surgery. Adv Ther. 2019;36(9):2515-2527.
8. Dorairaj S. Corneal endothelial cell changes after phacoemulsification combined with excisional goniotomy with the kahook dual blade or istent: prospective fellow-eye comparison. Poster presented at: 37th Congress of the European Society of Cataract and Refractive Surgeons; September 14-18, 2019; Paris, France.