Eyeworld

EW FEATURE 60 Products that could change how you practice • September 2018 AT A GLANCE • The role of cerebrospinal fluid pres- sure on glaucoma has been well es- tablished in medical literature within the last 10 years, but how to apply that knowledge to help patients has not yet made it to the clinic. • The imbalance between IOP and cerebrospinal fluid pressure in glaucoma can cause cupping of the optic disc and disruption of axonal transport, leading to damage of the optic nerve. • A team developed a set of goggles that essentially creates a vacuum over the eye, allowing on-demand, titratable IOP-lowering effects. • Proof-of-concept and in-human trials have been conducted, and a multicenter clinical trial is expected to begin within a year. by Liz Hillman EyeWorld Senior Staff Writer John Berdahl, MD, Vance Thompson Vision, Sioux Falls, South Dakota, published his first paper on the role of CSF pressure and glaucoma a decade ago. 1 Dr. Berdahl first got the idea about the role of cerebrospinal fluid pressure in glaucoma while scuba diving with his wife. With several hundred millimeters of mercury pressing on his body, including his eyes, he thought, why don't scuba divers get glaucoma? It's because that same pressure is applied all over the body, he reasoned. So was it possi- ble that people with glaucoma had something going on with their CSF pressure and IOP? Conducting research, Dr. Ber- dahl and coinvestigators found that patients with various forms of glau- coma do indeed have an imbalance of IOP and CSF (intracranial) pres- sure, which causes cupping of the optic disc resulting in nerve damage over time. This, Dr. Berdahl said, can explain why even patients with low IOPs can still develop glaucoma (they might have an even lower CSF pressure) and why those with high IOPs might not develop glaucoma (they have an elevated protective CSF pressure). "Clearly, we've been missing a big picture in glaucoma for a long time," Dr. Berdahl said. "In the United States, 30% of patients who have glaucoma never have a high eye pressure, and of those who have a high eye pressure, only 10% of them over 5 years go on to develop glaucoma. The story isn't just about eye pressure in isolation. We think it is eye pressure relative to cerebrospi- nal fluid pressure that is the un- derlying cause of disease. If that is the underlying cause of the disease, how do we use that information to develop technologies that can help people?" Dr. Berdahl's initial paper in 2008 has since been cited nearly 300 times, indicating strong research and support to this theory in the academic and scientific field. "On the scientific side, it's been millions of dollars, and hundreds of studies around this topic have been performed," Dr. Berdahl said, pointing out that he thinks most ophthalmologists think this rela- tionship is true. At a medical meet- ing 5 years ago, Dr. Berdahl said the audience was asked "Do you think A shift in the thinking of what causes glaucoma, a chance article about astronauts, and a company developing IOP-lowering goggles was born T o say that treatment for glaucoma has undergone a revolution within the last decade is an under- statement. There are new surgical options (several considered microinvasive glaucoma surgery [MIGS]) and new drug targets on the market. While there are surgical options and medications still in the pipeline, there is also a nonsurgical and nonpharmacologic option that could offer first-of-its-kind, on-de- mand, titratable IOP lowering—and its use could be as simple as strap- ping on a pair of goggles. Currently dubbed Balance Goggles (Equinox, Sioux Falls, South Dakota), the idea is that the gog- gles create a vacuum over the eye to lower eye pressure. The concept of this product was born out of the idea that it's not just IOP in glauco- ma that causes damage to the optic nerve, but that it's an imbalance between IOP and cerebrospinal fluid (CSF) pressure, and by decoupling these two pressures, a new therapeu- tic option would emerge. CSF pressure plays a role in glau- coma pressure—yes or no?" About 95% said yes. Russell Swan, MD, Vance Thompson Vision, Bozeman, Mon- tana, said when he was in residency 3–4 years ago the concept of CSF pressure in glaucoma was intro- duced but not widely discussed. Now, he added, over the last 1–3 years, he thinks there is a lot of dis- cussion and a lot of journal articles about it. "I think there is fairly unifying agreement that it plays a significant role," Dr. Swan said. "I think people are aware of it. I think they think it's true, and they don't have any idea what to do with that information," Dr. Berdahl said. "[Currently,] we don't get CSF pressures. We don't obtain them with spinal taps on glaucoma patients, so we're not getting that information on the front end, and even if we did, what do we do about it? We would lower eye pressure like we always do." There is not a practical, clinical application for this information—at least not yet. Six years passed after Dr. Ber- dahl got the idea about the role of CSF pressure and glaucoma. During that time he was primarily thinking about how to measure CSF pressure noninvasively. Then, while reading an article about the visual loss that astronauts faced with long-term spaceflight, Dr. Berdahl thought he knew why a percentage were losing vision. "It's the opposite of glaucoma, where CSF pressure is higher than eye pressure," he said. This led him to think that if pressure could be added to the eye, maybe the pressure differential across the optic nerve head could be balanced. "How could we do that?" he wondered. "You could push on the eye with a thumb or something to raise the eye pressure, but maybe you could put on a pair of goggles and pressurize them. … Those goggles will essentially pressurize the eye, and the pressure in the eye would go up. … Then I thought, why couldn't we depressurize the eye, creating a vacuum." As a physics major, Dr. Berdahl said this idea is a simple applica- tion of Pascal's law and hydrostatic physics. "The goggles act by changing atmospheric pressure," explained Malik Kahook, MD, director of the glaucoma service and glaucoma fellowship, Slater Family Endowed Chair in Ophthalmology, University of Colorado, Aurora. "The localized suction allows for control of the atmospheric pressure in and around the eye, potentially leading to a new set point pressure between the eye and the CSF pressure present in the optic nerve. In the case of suction, this may lead to a rebalance of the translaminar pressure (pressure on either side of the lamina cribrosa) and ease stress on the axons travel- ing through this space. In the case of added pressure, the rebalancing of translaminar pressure is intended Noninvasive, nonpharmacologic, nonsurgical glaucoma therapy " Drops and prior surgical procedures are effective at lowering IOP to a certain level, then for those who need additional IOP lowering, I think the goggles would be a great option. " —John Berdahl, MD

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