Regulating IOP in space-and redefining glaucoma

Take-home message: John Berdahl, MD, is the developer of Balance Goggles, eyewear intended to help regulate the pressure inside the eye.

By Michelle Dalton, ELS; Reviewed by John Berdahl, MD

Sioux Falls, SD-Nine years ago, John Berdahl, MD, was on a scuba diving trip with his wife, and had gone down about 30 feet or so, he recollects.

Dr. Berdahl“When you’re at 30 feet, there’s 760 mm Hg put everywhere on your body,” he said. “Considering we believe that any IOP above 21 mm Hg is abnormal, I began wondering how I could tolerate 760 mm Hg.”

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It was that moment when Dr. Berdahl began to think of glaucoma not as a disease confined solely to the ocular system, but as a disease of pressure differences throughout the body. The body uniformly experiences these pressure increases during scuba diving; since pressure rises are not confined to one area the entire body negates the increase.

“We’ve previously thought of glaucoma as a pressure inside the eye, not a relative-pressure-to-something-else disease,” Dr. Berdahl said. He began exploring (retrospectively) the relationship between IOP and cerebrospinal fluid (CSF) pressure, and others have confirmed the initial hypothesis.

Dr. Berdahl’s studies have been retrospective in nature, identifying people who have had spinal taps who also have glaucoma. He found CSF to be significantly lower in primary open-angle glauoma patients compared to the CSF levels in nonglaucomatous controls.¹ Similarly, he found intracranial pressure is lower in POAG and normal tension glaucoma, but elevated in ocular hypertensives.²

Researchers in Germany and China have done prospective studies with findings consistent with Dr. Berdahl’s.

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“It really may be that glaucoma is the imbalance between two pressures, not an overall increase in intraocular pressure. We still have work to do to prove that, but it's emerging to be true that that's the case,” he said.

The NASA angle

A recent NASA survey found almost 60% of astronauts experience vision issues after various missions, including short-term (90 days) in microgravity environments on Earth. Dr. Berdahl had read that astronauts are developing papilledema-a swelling of the optic nerve; in glaucoma there’s a cupping of the optic nerve.

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“So, in essence, in space the optic nerve head bows forward, whereas on Earth, the optic nerve bows backward,” he said. “Gravity helps pull the cerebrospinal fluid down into your spinal column. In space, however, the fluid redistributes ‘up’. Space reverses what we expect-the CSF pressure is higher than the IOP since the pressure gradient has been reversed.”

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Vision problems among astronauts are one of the reasons why the National Space Biomedical Research Institute (NSBRI, Houston, Texas) Industry Forum launched the ‘Vision4Mars’ Challenge. This challenge launched in November 2014 and is concentrated on identifying ophthalmic companies that are developing diagnostic tools to help understand and treat the visual alterations that many astronauts experience during space flight. NASA has stated its intention to send a manned craft to Mars in 2030.

Dr. Berdahl’s company, Equinox, will develop Balance Goggles, a “simple and comfortable pair of eye wear intended to help regulate the pressure inside the eye,” NSBRI said in announcing its grant to the company.

“These vision issues are a big deal to NASA and the NSBRI,” Dr. Berdahl said. “It’s a top health concern among astronauts-along with muscle loss and bone demineralization and ionizing radiation.”

Equinox

Dr. Berdahl launched Equinox, LLC, in 2014 to commercialize the goggles, he said, and has long-term plans to submit the goggles for Food and Drug Administration approval.

“The vernal and autumnal equinox is when day is exactly as long as night. We’re trying to ensure an equal balance between CSF and IOP, so the company name just made sense,” he said. “We have working prototypes of the goggles; we’ve done some proof of concept work. The grants we’ve received are now going to allow us to move into first-in-man studies, hopefully within the next 6-9 months.”

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Dorit Donoviel, PhD, deputy chief scientist for NSBRI and Industry Forum said Equinox’s device will “gently push on the exterior of the eye to stabilize the internal pressure within the eye by building mild pressure-regulating goggles.”

“We’re either applying a vacuum or applying pressure to equalize the internal IOP,” Dr. Berdahl said. People who wear the goggles can increase the ambient air pressure or create a “bit of a vacuum suction” that essentially lowers or increases the pressure in front of the eye, with the hope that those pressure changes are carried into the eye, he said.

The goggles will need to be worn for a specific amount a time in order to alleviate the pressure differential that may be causing the visual problems observed in some astronauts. The next round of trials should address the length of time necessary to wear the goggles for the eye to equalize itself.

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“This technology has the potential to benefit the millions of glaucoma patients around the world who do not respond to or cannot take the medication,” Dr. Donoviel said. “By dialing in a desired pressure in the eye and mechanically adjusting the goggles, patients can avoid surgery or the side effects of medication.”

By thinking of glaucoma as a metabolic disease, wearing the goggles should help equalize the pressures and remove the metabolic waste, Dr. Berdahl said. The current hypothesis suggests wearing the goggles for as little as 6 hours a day might be able to mitigate the pressure effect.

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But like all new concepts, Dr. Berdahl is prepared should his theory prove incorrect.

“Any time there’s new thinking, there's a high chance that you're wrong,” he said. “What we're really focused on is trying to ask answerable questions and answer them honestly so that we can determine if we've got real solutions here or not.”

References

1.     Berdahl JP, Allingham RR, Johnson DH. Cerebrospinal fluid pressure is decreased in primary open-angle glaucoma. Ophthalmology. 2008;115:763-768.

2.     Berdahl JP, Fautsch MP, Stinnett SS, Allingham RR. Intracranial pressure in primary open angle glaucoma, normal tension glaucoma, and ocular hypertension: A case–control study. Invest Ophthalmol Vis Sci. 2008;49:5412-5418.

John Berdahl, MD

E: john.berdahl@vancethompsonvision.com

Dr. Berdahl has financial interests with Equinox.