Intracranial pressure levels may be a critical factor in glaucoma
Key takeaways:
- Glaucoma may be a result of two pressures: IOP and intracranial pressure.
- When one pressure is high and the other is low, it results in ganglion cell proptosis, leading to glaucoma.
KOLOA, Hawaii — Intracranial pressure may be just as critical of a factor in the progression of glaucoma as IOP, according to a speaker here at Hawaiian Eye 2025.
“We spend a lot of time arguing about the facts, but not trying to discover the truth,” John P. Berdahl, MD, said in a presentation that earned him Speaker of the Day. “The common belief is that glaucoma is a one-pressure disease ... I would submit that the more likely truth is that glaucoma is a two-pressure disease: A balance between intraocular pressure and intracranial pressure, or [cerebrospinal fluid (CSF) pressure], across the optic nerve head.”
Berdahl noted that while IOP impacts the optic nerve, intracranial pressure (ICP) travels through the optic nerve to the back of the eye, making its role in glaucoma likely. Evidence of this can be found in patients with idiopathic intracranial hypertension who often present with a swollen optic nerve. Having a high IOP against a low ICP results in a “net force that's generated and movement below the curve posterior,” according to Berdahl.
“You’re going to tell me that IOP matters, and CSF doesn’t? No way,” he said.
Data has shown that patients with normal tension or primary open-angle glaucoma have lower levels of ICP, while patients with ocular hypertension have higher levels of ICP. In addition, while IOP increases with age, Berdahl referenced a study finding that ICP began to decrease in patients aged 65 years.
In addition, a study that investigated the impact of the two pressures in primates found that subjects with raised ICP developed glaucoma, even when IOP remained normal.
Overall, the two pressures must be kept at normal levels for axonal transport through the optic nerve to flow freely. When these pressure levels are differentiated, it may result in cupping or visual field loss.
“If you increase the intraocular pressure, or you decrease the intracranial pressure, axonal transport stops or slows at the level of [the] lamina cribrosa, and the metabolic means of those individual ganglion cells are not met,” Berdahl said. “Those individual ganglion cells undergo proptosis one by one, and we end up with glaucoma.”
References:
- Berdahl J, et al. IOVS. 2008:10.1167/iovs.08-2228.
- Fleischman D, et al. PLoS One. 2012:10.1371/journal.pone.0052664.
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Berdahl J. A tale of two pressures. Presented at: Hawaiian Eye 2025; Jan. 18-24, 2025; Koloa, Hawaii.