Decades of progress

[caption id="attachment_8403" align="alignnone" width="325"] Reay H Brown[/caption] With three minimally invasive glaucoma surgery (MIGS) implants now FDA approved, and several more nearing market, the surgery is playing an ever-growing and earlier role in glaucoma treatment, Reay H Brown MD told the 2017 ASCRS•ASOA Symposium & Congress in Los Angeles, USA. The total MIGS market now exceeds $3billion and is growing exponentially. However, many studies suggest that in combined phaco-MIGS procedures the bulk of intraocular pressure (IOP) lowering may be due to phaco, with devices such as the iStent® (Glaukos) and CyPass® (Alcon) increasing the effect. While the therapeutic impact is not trivial – MIGS-treated eyes generally require fewer drops for IOP control after surgery, and are more likely to be drop-free than phaco-only eyes – MIGS has not ‘solved’ glaucoma in the same way that phaco solved cataract, said Dr Brown, who delivered this year’s Charles D Kelman Innovator’s Lecture in recognition of his decades of development of glaucoma surgery techniques. PUMPING ACTION MIGS device performance might be considerably improved by adding pumping action, Dr Brown said. He is currently working with researchers at the Georgia Institute of Technology in Atlanta, USA, to develop cilia pumps driven by rotating magnets. These cilia can be very small, of the order of 100 microns long, and have been shown to generate significant power in early development. “Nature’s pump is cilia and they are everywhere,” he said. Considerable research will be needed to bring such pumps to life, Dr Brown said. He expects the process to take years, as it already has to develop today’s MIGS devices. What MIGS has done is change the glaucoma treatment paradigm. By demonstrating that a viable market exists for glaucoma surgery it is attracting the money, competition and skills needed to further develop it. “One of the finest things about MIGS is it gives us hope that we will finally solve glaucoma,” Dr Brown said. KELMAN THE INSPIRATION Both MIGS and phaco look obvious in retrospect, but both took decades to take hold, Dr Brown noted. Throughout the 1970s and 1980s, phaco was resisted, especially in academic circles. “Kelman is the inspiration, he really solved cataracts. MIGS is more of a team sport and glaucoma is not yet solved,” he said. Dr Brown recounted his own involvement with MIGS, which dates back to his residency beginning in 1979. During long nights on call at the Wilmer Eye Institute at Johns Hopkins University, Baltimore, Maryland, USA, he found a rich literature showing trabeculotomy and goniotomy were very popular and successful in controlling IOP in adult open-angle glaucoma in Europe. “I wondered, ‘Why aren’t US surgeons doing this?’ If the resistance is in the trabecular meshwork, angle surgery makes sense to restore outflow.” Dr Brown’s attempts to improve glaucoma surgery include using a trephine developed for vitrectomy to punch holes in the trabecular meshwork into the subconjunctival space from the inside through a 20-gauge incision. However, flow was too fast or too slow, and a device was needed to keep the channel open, but none existed in the 1980s. In 1994, Dr Brown patented the glaucoma tack with Keith Thompson, which drained aqueous directly from the anterior chamber. “The idea was to make glaucoma a microfluidics problem, not a conjunctival wound healing problem,” he said. The two major eye device companies looked at it but passed – though the concept is now in development by MicroOptx and scheduled to begin FDA human trials. RESTORING OUTFLOW Work with his wife, Mary Lynch MD, led to 360-degree suture trabeculotomy, which achieved a 90% success in one operation. Later, work with Robert Stegmann MD on viscocanalostomy inspired them to invent a T tube insert called the EyePass that restores outflow in both directions. What really spurred current interest in glaucoma surgery was the insight of device development executives to target MIGS as an eye drop replacement for mild to moderate glaucoma rather than a trabeculectomy replacement for refractory patients. In the USA alone, that increased the potential market from 75,000 procedures annually to 800,000, making MIGS commercially viable, Dr Brown said. Reay H Brown: reaymary@comcast.net