Every glaucoma patient should be offered MIGS with cataract surgery
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I was honored to give the Stephen A. Obstbaum, MD, Lecture at the 2022 American Society of Cataract and Refractive Surgery meeting and the Ridley Medal Lecture at the 2023 Snowmass Retina & Eye meeting.
For both lectures, I chose to share my thoughts on the use of MIGS and advanced-technology IOLs in the management of patients with combined cataract and glaucoma. In this perspective, I will share the core thoughts presented in those lectures. I disclose that I consult widely in both these fields.
I have written before that cataract surgery is a vision-restoring modern-day miracle, having improved vision in more than 500 million eyes globally in the past 25 years, according to Market Scope. Less well known to many, according to Medicare and IRIS Registry data, is that 20% of patients who present for cataract surgery in the U.S. have either ocular hypertension under treatment with glaucoma drops or mild to moderate glaucoma with confirmed optic nerve damage.
Level 1 evidence supports as fact that cataract surgery alone, whether by phacoemulsification or as an extracapsular cataract extraction procedure, reduces IOP significantly. This finding makes cataract surgery the most common glaucoma surgery performed today. My partner Tom Samuelson, MD, a fellowship-trained glaucoma specialist, the late Brooks Poley, MD, an employee medical ophthalmologist in our practice, and I reported a retrospective review of several hundred patients in our practice with combined cataract and glaucoma in 2007 that confirmed this fact. We found IOP reduction after phacoemulsification with IOL implantation was significant, sustained and proportional to the preoperative IOP. Patients with IOPs at the time of cataract surgery of 23 mm Hg to 31 mm Hg achieved a mean IOP reduction of 7 mm Hg, which was sustained for an average of 4.5 years. In both the multicenter prospective Glaukos pivotal trial for the iStent and the Ivantis pivotal trial for the Hydrus microstent (Alcon), the control group patients with cataract surgery and IOL implantation alone achieved IOP reductions of 6.9 mm Hg and 5.3 mm Hg 2 years after surgery, confirming our findings. Multiple other clinical trials from centers around the world agree — cataract surgery alone with or without IOL placement is a powerful glaucoma operation.
Tom Samuelson and I believe the mechanism that lowers IOP is simply mechanical. The natural lens increases in thickness with age from 3.5 mm to 4 mm in a person’s 20s to more than 5 mm by their 70s. This increased thickness of the natural lens results in outflow angle narrowing and a progressive reduction in facility of outflow. Cataract surgery restores a deep and open outflow angle and results in an increase in facility of outflow, significantly reducing IOP.
Between 1980 and 2000, a common procedure for me to perform in the patient presenting for surgery with glaucoma and cataract was a combined trabeculectomy, cataract removal and IOL implantation. Beginning about 2000, I began to simply perform cataract/IOL surgery on these patients. With modern small-incision clear corneal cataract surgery, the conjunctiva was spared, making a later trabeculectomy safer and more successful. I was surprised to find that less than 1% of my patients with mild to moderate glaucoma ever required a trabeculectomy or tube shunt. The majority were well managed with clear corneal phacoemulsification alone plus adjunctive therapy with topical medication.
The important prospective 5-year study of trabeculectomy and tube shunt surgery for glaucoma published by Gedde and colleagues in American Journal of Ophthalmology in 2012 confirmed that while both procedures were highly efficacious, resulting in IOPs of 14.4 mm Hg and 12.6 mm Hg on just more than one topical medication at 5 years, there was a significant failure rate, a high complication rate and a high reoperation rate. A safer glaucoma procedure was a significant unmet need, especially for the patient with ocular hypertension or mild or moderate glaucoma. The response was the development of several minimally (micro) invasive glaucoma surgery procedures. Ike Ahmed has defined MIGS as causing minimal tissue disruption, resulting in rapid patient recovery, and being both effective and safe with minimal intraoperative or postoperative complications. The first MIGS procedure to achieve this goal was the iStent, which reduced IOP and topical glaucoma medication burden when compared with cataract surgery alone with no increase in complication rate. We now have multiple MIGS options, as is discussed in the accompanying cover story.
Who is a candidate for MIGS? For me, it is every patient who presents for cataract surgery with treated ocular hypertension, mild glaucoma or moderate glaucoma. MIGS is an operation that can and should be a part of every cataract surgeon’s repertoire. With more than 4 million cataract surgeries per year being performed in the U.S., we would expect there to be more than 800,000 MIGS procedures as well. Market Scope data in 2021 confirm that we are well below that number. The reason is that in the same survey of U.S. cataract surgeons, only 46% performed MIGS, and even more troubling to me, 38% had no plans to offer MIGS to their patients in the future. While controversial to some, I believe every patient on glaucoma medication deserves to be offered a MIGS procedure along with their cataract surgery. We U.S. eye surgeons as a group can and must do better here.
Now to the even more controversial. What about advanced-technology IOLs and refractive cataract surgery in glaucoma patients? The problem: Glaucoma is progressive, and even mild glaucoma reduces contrast sensitivity. Many early-generation presbyopia-correcting advanced-technology IOLs caused a significant reduction in contrast sensitivity, resulting in surgeon hesitation to offer them to glaucoma patients. However, today, we have several advanced-technology IOLs that result in minimal to no loss of contrast sensitivity. These include all the monofocal toric IOLs, the Light Adjustable Lens (RxSight), the Crystalens (Bausch + Lomb), the IC-8 Apthera (AcuFocus), several extended depth of focus lenses and even some trifocal IOLs. I believe every patient with mild to moderate glaucoma who presents for cataract surgery also deserves the opportunity to receive an advanced-technology IOL. Here again, current data suggest we surgeons are not performing well in the U.S.
In summary, the vision-restoring modern-day miracle of cataract/IOL surgery is also a very effective glaucoma operation. Adding a low- to no-risk MIGS procedure to the surgical plan for a patient with combined cataract and glaucoma further reduces IOP and medication burden. It is appropriate to offer this option to all patients with treated ocular hypertension, mild glaucoma or moderate glaucoma who present for cataract surgery. Refractive cataract surgery with proper advanced-technology IOL selection can also be offered to nearly all patients with glaucoma and cataract. Even the patient with severe glaucoma can benefit from having their astigmatism managed. Offering MIGS and refractive cataract surgery to every patient with ocular hypertension, mild glaucoma or moderate glaucoma who presents for cataract surgery will benefit patients, providers, industry, society and even payers by enhancing visual performance and reducing long-term glaucoma damage, medication burden and visual disability.
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