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    Regulating IOP in space—and redefining glaucoma

    An idea sprung from a scuba diving trip may have benefits for astronauts and glaucoma patients alike

     

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

     

    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.

    John Berdahl MDDr. 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.

    Next: Equinox

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