MIGS a promising opportunity for patients and physicians

Issue: February 25, 2012

Richard L. Lindstrom

A safe and effective, minimally invasive glaucoma device is, in my opinion, a major unmet need in ophthalmology. Many are currently in clinical trials and early commercialization around the world, and one, the Glaukos iStent, has received a favorable review by the U.S. Food and Drug Administration Ophthalmic Devices Panel, but none are yet on the market in the U.S.

Glaucoma is the leading cause of blindness in the developed world. Globally, 65 million people have glaucoma. It is estimated that less than 50% who have glaucoma have been diagnosed and fewer yet are receiving effective treatment. In the U.S., 7 million visits a year to a physician’s office are for the management of glaucoma. To put the economics of glaucoma in perspective, the global cost for the treatment of cataract is estimated at about $2.2 billion and for age-related macular degeneration, $3.2 billion. Glaucoma dwarfs these two at an estimated annual treatment cost of $5.8 billion.

The primary therapy is topical pressure-reducing drops, and the glaucoma medication category is by far No. 1 in ophthalmic pharmaceutical company revenues. The good news is that we have several safe and effective topical medications for the treatment of glaucoma. The bad news is that our patients rarely take them properly. While compliance is better with reduced dosing rates, even at one drop a day some studies suggest that patients in compliance number only about 50%.

Many have suggested that glaucoma should be a surgical disease. Laser treatments including argon laser trabeculoplasty and selective laser trabeculoplasty are quite safe and can be effective, but their efficacy tends to diminish with time, reducing their effectiveness for a lifelong problem. Our classical surgeries, trabeculectomy and tube shunt, while quite effective, carry a relatively high and lifelong complication rate. The recent Tube Vs. Trabeculectomy Study emphasized that fact, with sight-threatening complications in 30% to 60% of patients, respectively. So, we definitely need something better.

For the cataract surgeon, removal of the natural lens with phacoemulsification and placement of an IOL is proving to be quite effective in lowering IOP when elevated. Our studies at Minnesota Eye Consultants show that a patient with a preoperative pressure near 25 mm Hg can expect a 6 mm Hg to 8 mm Hg drop in IOP with cataract surgery alone. These results are being repeatedly confirmed, and most impressive to me are the data from the prospective, well-controlled clinical trial by Glaukos that showed an 8.4 mm Hg drop in IOP with cataract surgery alone.

Minimally invasive cataract surgery (MICS) appears to be in itself minimally invasive glaucoma surgery (MIGS). However, the patients in our studies still required, on average, one topical medication after surgery to maintain an IOP that was satisfactory to the treating surgeon. In addition, typical postoperative pressures were between 15 mm Hg and 21 mm Hg. This takes us back again to concerns with topical medication compliance. Ideal would be an IOP less than 15 mm Hg off all medications. At this pressure, if maintained 24 hours a day, according to the clinical trials funded by the National Eye Institute, the chance of progressive glaucoma damage is very low.

To achieve this outcome, it appears that we need to do another procedure at the time of cataract surgery. For the patient with cataract and elevated IOP and glaucoma, the combination of MICS plus MIGS to me holds the greatest promise for a safe and effective way to achieve long-term IOP control with minimal topical medication burden. This is a common practice, approaching 20% according to Centers for Medicare and Medicaid Services statistics, or about 600,000 patients a year in the U.S. alone and nearly 4 million annually worldwide.

As I read study after study, the typical glaucoma patient when taken off their medications has a mean washout IOP around 25 mm Hg. In addition, the efficacy of all therapies, medical and surgical, seems to be proportional to the pretreatment IOP. Higher pressures get greater pressure-lowering responses. Thus, my admittedly very simplistic analysis is that we need a MIGS that can generate a 10 mm Hg to 12 mm Hg drop in IOP reliably, or for the cataract patient, one that can give a 4 mm Hg to 6 mm Hg boost to the 6 mm Hg to 8 mm Hg drop achieved by MICS itself.

As the MIGS alternatives work their way toward the marketplace, the outcome goals I will be analyzing, in addition to extraordinary safety, are the percent of patients with an IOP reduction of greater than 10 mm Hg, the percent who achieve an IOP less than 15 mm Hg, and the average medication burden required to achieve these outcomes. The NEI-funded prospective clinical trials have shown us that every IOP reduction counts in protecting a patient from progressive glaucoma damage, but what the patient wants is his or her glaucoma cured, and to me that requires an IOP of less than 15 mm Hg off medications 24 hours a day. If we can achieve this outcome in the majority of patients with a minimal complication rate, I see glaucoma surgery volumes exploding.

By 2020, I project the 8,000 or so anterior segment surgeons in the U.S. will each need to manage each year at least 500 cataract surgeries, 250 refractive surgeries, 200 or more glaucoma procedures, 100+ other procedures including pterygium and the like, as well as a significant number of intraocular injections for AMD, as our retina colleagues collapse under the growing demand for this service. The typical anterior segment surgeon/comprehensive ophthalmologist will find himself or herself in the OR more than the office, changing the current norm of 1 day a week in the operatory to 2 or 3 days. Those with good skills will be in high demand, and the ever improving outcomes and growing patient-shared responsibility for the cost will, in my opinion, serve as a basis for a very rewarding career.