In my solo anterior segment practice, about 20% to 25% of my cataract patients undergo a minimally invasive glaucoma surgery (MIGS) procedure at the time of cataract surgery. For those patients with glaucoma, cataract surgery presents a unique, one-time opportunity to also achieve a reduction in IOP and potentially reduce or eliminate the number of topical drops they need.

I consider MIGS to be well within the wheelhouse of any anterior segment surgeon. I personally implant the iStent (Glaukos), Hydrus Microstent and Xen (Allergan) devices and perform Kahook Dual Blade (KDB) goniotomy (New World Medical) and selective laser trabeculoplasty (SLT).

Despite the advantages for patients and practices, many cataract surgeons have not adopted MIGS. According to the most recently published ASCRS Clinical Survey, nearly half of respondents (48%) don’t perform any glaucoma surgery, including MIGS.¹ Only about 22% said they were performing Schlemm’s canal-based surgery, which is arguably the best starting point for an anterior segment surgeon.

Here, I explain why more cataract surgeons should consider performing MIGS procedures and how to get started.

REASONS TO START MIGS

Slow glaucoma progression

Cataract surgery itself reduces IOP, but MIGS procedures have been shown to reduce IOP more than cataract surgery alone, including a higher likelihood of achieving a greater than 20% reduction in IOP.^2,3 Moreover, MIGS can help patients avoid more invasive glaucoma surgeries down the line. Rhee et al recently showed that patients implanted with a common first-line MIGS device, the Hydrus Microstent (Ivantis), had a three-fold reduction in their risk of undergoing a secondary surgical intervention within 4 years of cataract surgery.⁴ That’s a great service to patients.

Limit topical medications

This IOP-lowering benefit is achieved with the same or — in most cases — fewer topical medications. There are many good reasons to try to eliminate or reduce the number of medications at the time of cataract surgery, even if a patient is well controlled on topical drops.

As someone who cares about visual quality outcomes after cataract surgery, I am always concerned about the impact of chronic topical medications on ocular surface health. The preservatives in glaucoma drops disrupt tear film stability and ocular surface integrity, leading to fluctuating vision and abnormal Ocular Surface Disease Index (OSDI) scores in about half of all glaucoma patients.⁵ Another study found that more than 30% of topically-treated glaucoma patients have abnormal tear break-up time and punctate keratitis and 42% have a dry eye diagnosis (Figure 1).⁶ In particular, prostaglandin analogues, our first-line glaucoma therapeutic class, have been closely associated with meibomian gland dysfunction (Figure 2).⁷ The rate of OSD rises with the number of topical medications.^5,6 In addition to the potential effects on cataract surgery outcomes and satisfaction, glaucoma patients with OSD have more medication side effects,⁸ worse quality of life⁶ and a higher risk of glaucoma progression.⁹

Financial benefit for patients

Offering MIGS at the time of cataract surgery is financially beneficial. These patients get a significant positive impact of lower IOP without much increase in their out-of-pocket costs for surgery — and possibly with a reduction in future outlays for medications, as well. In the United States, we can’t perform MIGS as a standalone procedure in most cases, so cataract surgery really represents the only opportunity for patients to benefit from MIGS.

Makes sense for the practice, too

Medicare and other third-party payer coverage for MIGS at the time of cataract surgery is by now well established across the country. Performing more MIGS procedures increases the revenue per patient but, unlike many other new services we might offer in ophthalmology, the economic barriers to entry are very low.

There is no capital investment in lasers or other treatment devices. You do not need to hire more staff. The needed diagnostic equipment (OCT, ocular perimetry, indirect gonioprism) probably already exists in the practice. And, no matter your practice size, if you are performing cataract surgery, you already have a significant population of glaucoma patients in the practice.

HOW TO GET STARTED

First, use a canal-based procedure

It is helpful to set a goal of learning to use multiple MIGS devices so that you can take advantages of the nuances and varying indications for each to target different types of patients. At first, though, just focus on becoming comfortable with one. Focusing your attention on the learning curve of one device will give you and your team the confidence to add more MIGS devices in the near future.

The best place to start is with one of the ab interno, canal-based MIGS procedures that open the eye’s natural drainage channel. I started 9 or 10 years ago with the iStent, which has since gone through several design iterations and now involves simultaneous injection of two tiny stents. With such a long history in the United States, there is lots of information available about injection and positioning of the iStent. The more recent canal-based option is the Hydrus Microstent. For both of these devices, the postoperative care course and the safety profile are similar to cataract surgery alone.^2,3

I recently began implanting the Hydrus Microstent after hearing some colleagues talk about the results of the HORIZON study. In this randomized, controlled trial, more than three-quarters of Hydrus patients achieved a significant reduction in IOP and 65% were medication-free at 4 years (Figure 3).⁴ The device is 8 mm long and about the size of an eyelash. It is inserted through a clear corneal incision and guided through the trabecular meshwork (TM) into Schlemm’s canal, where it scaffolds approximately 90% of the canal (Figure 4).

Although there is a learning curve for new users, the size of the device makes placement very straightforward. If you are not in Schlemm’s canal, you’ll know right away because patients will express discomfort. Additionally, if the stent begins to dive downward, rather than remaining parallel with the TM, that is another indication that it is not in the right position. Simply back out and reinsert a couple of clock hours away.

To learn either of these devices, review journal articles and online videos, observe colleagues in surgery if possible and lean on your representatives from the manufacturers for guidance, education and wet labs.

Choose the right patients

For your first cases, I recommend choosing cooperative patients who are not too nervous and are not likely to be fidgety under topical anesthesia. Preoperatively, be sure to perform a good gonioscopic exam to ensure that the eye has a nice, approachable (not too shallow) angle. Myopes with no scar tissue or previous surgery in the angle often work best.

Consider your schedule

Add your first MIGS cases to the end of a cataract surgery day. This ensures they won’t slow down the schedule and that you do not feel the pressure of being rushed. Once you become comfortable with the procedure, MIGS adds just a few minutes to the cataract surgery time (and is reimbursed accordingly) so you can mix these cases throughout the schedule. Each surgeon will have their own learning curve trajectory. When I learned to use the iStent many years ago, the most challenging part was learning direct, surgical gonioscopy. After about 10 procedures my learning curve began to flatten out, and I slowly learned new aspects of performing surgery in the angle.

Next steps

Once you feel more comfortable with the angle and have mastered implantation of one or two MIGS devices, you can progress the learning curve. First, I suggest moving beyond the easy cases and allowing all your mild-to-moderate glaucoma patients to be candidates for MIGS if they are undergoing cataract surgery.

Next, you may want to learn a procedure that is indicated for more advanced glaucoma, such as the Xen gel stent implant, or gain experience combining MIGS procedures. For example, I like to perform a KDB excisional goniotomy in conjunction with either an iStent or Hydrus, because their mechanisms of action are complementary. The KDB has a foot plate that allows for a very precise, controlled excision of the TM, exposing the collector channels behind the TM and allowing aqueous to flow from the anterior chamber to Schlemm’s canal, which you have also stented open for effective drainage. This provides even greater IOP reduction for those who need it.

Patient conversations

I have found that patient acceptance of MIGS is very high and the conversation is an easy one, even when the patient comes in knowing nothing about glaucoma surgery. When I explain that MIGS can slow down progression of their glaucoma and may allow them to stop one or more of the drops they are currently using, most patients are enthusiastic — especially when they learn it can be billed to their insurance. We describe the stents as some of “the world’s smallest medical implants,” which almost universally “wows” the patient.

Handling the influx of referrals

MIGS has also been a practice-building procedure for me. When I started offering combined cataract-glaucoma surgery, we saw big changes in our referral patterns, including referrals from optometrists who had never sent me patients before and higher volumes from those who were already in my referral network. In some cases, there was initially trepidation that we would not only perform the surgery but try to take over patients’ routine glaucoma management. Once referring doctors saw they were getting the same patient back in the same time frame after cataract surgery — just with lower IOP — those concerns dissipated. In fact, I find that many referred patients come in now saying their doctor told them to ask me about the opportunity to have glaucoma surgery.

Although complications from MIGS are rare, it is important to educate referring doctors about what to watch for and to be available to discuss and quickly evaluate any complications that do arise.

CONCLUSION

MIGS is a professionally satisfying opportunity to help patients who have both cataract and glaucoma. Medically, it is the ideal choice for patients to reduce their dependence on ocular surface-damaging drops. With rates of glaucoma climbing and cataract surgery reimbursement falling, this is a great time to add MIGS to your practice. OM

REFERENCES

1. Highlights of the 2019 ASCRS Clinical Survey. American Society of Cataract and Refractive Surgery. https://supplements.eyeworld.org/eyeworld-supplements/ascrs-clinical-survey-2019 . Accessed December 21, 2020.
2. Samuelson TW, Sarkisian SR, Lubeck DM, et al. Prospective, randomized, controlled pivotal trial of an ab interno implanted trabecular micro-bypass in primary open-angle glaucoma and cataract: two-year results. Ophthalmology. Jun 2019;126:811-821.
3. Samuelson TW, Chang DF, Marquis R, et al; HORIZON Investigators. A Schlemm canal microstent for intraocular pressure reduction in primary open-angle glaucoma and cataract: The HORIZON Study. Ophthalmology. 2019;126:29-37.
4. Rhee, DJ. 4-Year Findings from the HORIZON Trial, American Glaucoma Society annual meeting, Feb 27, 2020. Washington D.C.
5. Fechtner RD, Godfrey DG, Budenz D, et al. Prevalence of ocular surface complaints in patients with glaucoma using topical intraocular pressure-lowering medications. Cornea. 2010;29:618-621.
6. Rossi GCM, Pasinetti GM, Scudeller L, et al. Risk factors to develop ocular surface disease in treated glaucoma or ocular hypertension patients. Eur J Ophthalmol. 2013;23:296-302.
7. Mocan MC, Uzunosmanoglu E, Kocabeyoglu S, Karakaya J, Irkec M. The association of chronic topical prostaglandin analog use with meibomian gland dysfunction. J Glaucoma 2016;25:770-774.
8. Denis P. Adverse effects, adherence and cost-benefits in glaucoma treatment. Eur Ophthalmic Rev. 2011;5:116-122.
9. Denis P, Lafuma A, Berdeaux G. Medical outcomes of glaucoma therapy from a nationwide representative survey. Clin Drug Invest. 2004; 24:343-352.

About the Author

Timothy D. McGarity, MD, is the owner of Restoration EyeCare in Columbia, Mo. Email him at tim@restorationeyecare.com.

Dr. McGarity reports no relevant financial relationships.