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Presenter: Minimizing disparity between intraocular, intracranial pressures can prevent glaucoma
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ATLANTA – In a special session here at SECO, John Berdahl, MD, theorized that glaucoma results when the difference between the cerebrospinal fluid and intraocular pressures is too great.
Berdahl said he evaluated 50,000 patients who had lumbar puncture over the course of 20 years and found that intracranial pressure (ICP), or cerebrospinal fluid (CSF) pressure, was lower in people who had glaucoma and higher in people with ocular hypertension.
John Berdahl
“You have a high IOP, but you have a high ICP to protect you,” he said.
Those with primary open-angle glaucoma had lower CSF pressure, and those with normal-tension glaucoma had even lower CSF pressure, he said.
Berdahl said groups in China and Germany repeated his studies prospectively, performing lumbar punctures in patients with glaucoma, and found the same thing.
“CSF pressure is pretty steady until you get about 65, then it starts to drop off,” he said. “At what age do people start to get glaucoma? Their eye pressure doesn’t go up, but their CSF pressure goes down.”
It is known that CSF pressure increases with body mass index. “That’s probably why glaucoma is protected with increasing weight,” Berdahl said.
He noted that data shows that low blood pressure, which is related to CSF pressure, may put you at risk for glaucoma.
“I believe IOP and CSF pressure are meant to work in concert,” Berdahl said. “If we can decouple IOP from CSF, we can better treat glaucoma.”
Berdahl presented an example: “In glaucoma, say an IOP of 16 mm Hg goes up to 22 mm Hg, and that the CSF pressure of 12 mm Hg goes down to 9 mm Hg; now the trans-laminar pressure difference is 13. What if we could decrease the pressure of the front of the eye, taking the 22 mm Hg down to 12 mm Hg so that the pressure gradient is only 3 mm Hg? Now we’re protecting that eye from glaucoma.”
He explained that atmospheric pressure is pressing down on the eye, a “cosmic thumb,” he said.
“We think maybe we could treat glaucoma with a pair of goggles that puts a little vacuum in front of the eye and relieves some of that atmospheric pressure,” Berdahl said. “Now we can treat glaucoma in a nonsurgical, nonpharmacologic, totally titrable way.
“If we can heal with physics instead of biology, we’re onto something,” he added.
Berdahl is a member of the Vision to Mars team, working with NASA to address ocular problems astronauts experience on long-term space missions.
He said that astronauts on the International Space Station are experiencing swelling of the optic nerve.
“It’s because in space there’s no gravity to pull the CSF down to the spine to lower the eye pressure,” he said. “With no gravity, CSF pressure goes up at eye level.”
He said these astronauts are experiencing VIIP: visual impairment and intracranial pressure.
“First, the globe is flattening,” Berdahl said. “That’s because the CSF pressure is high, and it’s pushing the back of the globe forward, leading to shorter axial length, which leads to hyperopic shift. Astronauts are given a pair of dialable hyperopic reading glasses so they can self tune themselves.”
They also experience choroidal folds and papilledema.
“This is a big deal to NASA,” he said. “I’ve been told this is their #1 health concern and #3 safety concern. If an astronaut can’t see, there are big problems. And until we solve this, we can’t figure out how to get a person on Mars.”
Berdahl is studying how to use goggles to raise astronauts’ IOP to minimize its difference from the CSF pressure in space.
“When you go scuba diving, you raise your eye pressure to 760 mm Hg,” he said, with no deleterious effects.
Applied to the general population, he envisions people would wear the goggles only at night to equalize pressure, like a C-PAP machine.
“But we need convincing science,” he concluded. – by Nancy Hemphill, ELS, FAAO
Disclosure: Berdahl is CEO and founder of Equinox, a company developing goggles to adjust IOP.
Reference:
Berdahl J. The sky's the limit – or is it?