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    Glaucoma may not be the disease you think it is

    Growing evidence supports IOP, CSF pressure differential


    Ocular hypertension

    The two-pressure model also explains ocular hypertension without glaucoma. These individuals have elevated IOP with a similarly elevated ICP that protects the optic nerve. Even though the absolute pressure on both sides of the lamina cribrosa is high, the normal pressure gradient allows for normal axonal transport.

    Testing the two-pressure model at the clinical level is difficult. Ophthalmologists and other vision specialists routinely measure IOP at the cornea. But the only currently available method to measure ICP is an invasive lumbar puncture.

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    Multiple research groups are working with animal models to develop noninvasive or less invasive methods to measure ICP, Dr. Berdahl continued.

    Other groups are investigating multiple pharmaceutical agents known to affect ICP or CSF pressure for potential to treat glaucoma.

    Dr. Berdahl is taking a different approach.

    About one-half of visitors to the International Space Station suffer from vision impairment and intracranial pressure (VIIP). In a normal environment, gravity pulls fluid into the lumbar column and slightly reduces ICP, he explained.

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    In a weightless or microgravity environment, such as the space station, CSF redistributes evenly throughout the cerebrospinal space, increasing ICP. In some astronauts, this increased ICP causes flattening of the eye, hyperopic shift, choroidal folds, optic disk edema, and impaired vision.

    Dr. Berdahl founded Equinox LLC to develop special goggles (Balance Goggles). The goggles use physics to counteract the increased ICP of weightlessness by increasing the external pressure on the eye, which raises IOP to restore the normal pressure gradient at the lamina cribrosa.

    “The goggles have a good shot at controlling eye pressure very precisely to counteract ICP,” Dr. Berdahl said.

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    “The same concept can be applied to glaucoma by reducing the atmospheric pressure on the eye, which reduces IOP and reduces the pressure gradient at the optic nerve,” he said. “Redefining glaucoma as a two-pressure pathology opens a lot of physical and pharmacologic pathways to diagnose, treat, and even prevent glaucoma.”

    Learn how the goggles concept was inspired by John P. Berdahl, MD, while on a scuba diving trip. Go to http://bit.ly/2aGZaFJ


    John P. Berdahl, MD

    E: [email protected]

    This article was adapted from Dr. Berdahl’s presentation at the 2016 meeting of the American Society of Cataract and Refractive Surgery. Dr. Berdahl has financial interests with Equinox.


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