“The relationship between blood pressure and glaucoma risk is complicated,” says ophthalmologist Yvonne Ou, M.D. of the University of California, San Francisco’s UCSF Medical Center. To help lower glaucoma risk, Ou sheds light on this important topic at the intersection of overall health and eye health.*

‘Moderation is key’

Both high blood pressure (hypertension) and low blood pressure (hypotension) can increase your risk of glaucoma. The adage “everything in moderation” is fitting, Ou says, when it comes to eye health, blood pressure level, and glaucoma risk.

• Very high blood pressure can raise internal eye (intraocular) pressure, or IOP, which can damage the optic nerve.
• Low to very low blood pressure is also problematic, however, because the optic nerve needs adequate blood flow, and low pressure inhibits that flow.

High blood pressure and glaucoma risk

Research doesn’t yet show conclusively that hypertension directly causes glaucoma, but we know that elevated blood pressure raises eye pressure, possibly because excess eye fluid is made and/or the eye’s drainage system is blocked or otherwise malfunctioning.

• That said, blood pressure needs to rise about 10 mmHg (millimeters of mercury) for eye pressure to rise 0.26 mmHg.
• Hypertension can also lead to hypertensive retinopathy, or damage to the retina and retinal circulation.

Ou reminds us, “[O]f course, high blood pressure increases the risk of heart disease and stroke, so it is crucial to treat,” regardless of its potential impact on vision.

Low blood pressure and glaucoma risk

Conversely, several large studies have shown that hypotension can raise glaucoma risk. This can happen through what’s called ocular perfusion pressure (OPP), which is blood pressure minus IOP.

• Low OPP can occur in people with naturally low blood pressure, as well as people overtreated for high blood pressure—”a real possibility,” Ou says, given today’s stricter rules for controlling blood pressure.

Hypotension can also be an issue at night when blood pressure naturally dips, as blood pressure and eye pressure fluctuate throughout the day.

• Optic nerve damage can occur overnight if blood pressure drops while IOP rises.

‘Talk with your doctors’

Since hypertension and hypotension are both glaucoma risk factors, Ou emphasizes the need to speak with both your eye doctor and internist or primary care doctor if blood pressure is an issue.

• Inform your eye doctor of any high blood pressure and related medications, especially if you have glaucoma. Systemic (whole-body) blood pressure medicines, or beta-blockers, can also decrease heart rate. On top of this, a common glaucoma medication is a beta-blocker eye drop. Using both concurrently could have unwanted side effects.
• People with chronic kidney disease also need to be aware that blood pressure can fluctuate during dialysis, causing low OPP if blood pressure dips. Dialysis patients with glaucoma need to discuss their conditions with their eye doctor and kidney specialist. It’s possible for dialysis to be adjusted to lower optic nerve risk.

Ou advises not allowing your blood pressure to get too high or too low. Research is ongoing to better understand the relationship between blood pressure and glaucoma, so doctors can better guide patients.

*Ou, Y. (2021, July 7). Blood Pressure and Glaucoma. BrightFocus Foundation. https://www.brightfocus.org/glaucoma/article/blood-pressure-and-glaucoma