New research may have unlocked a mystery of why glaucoma continues to worsen in some patients even when their intraocular pressure (IOP) is well controlled: low minimum blood pressure.

The study found patients with lower 24-hour systemic blood pressure, and particularly lower minimum mean arterial pressure, systolic blood pressure, and diastolic pressure measured by ambulatory monitoring experienced faster rates of structural deterioration of glaucoma than those whose pressures remained more moderate.

“Our findings suggest that 24-hour ambulatory blood pressure monitoring may help identify a subset of glaucoma patients at higher risk of structural progression, particularly those progressing” at low IOP, said Davis Zhou, MD, an ophthalmologist at Bascom Palmer Eye Institute at the University of Miami, Miami. “While ambulatory blood pressure monitoring is not currently standard practice in glaucoma care, it may be reasonable to consider in patients who continue to progress despite apparently adequate” control of IOP.

Zhou presented the research at American Glaucoma Society (AGS) 2026 Annual Meeting.

The prospective cohort study included 79 glaucomatous eyes of 42 patients enrolled in the Vascular Imaging in Glaucoma Study at Bascom Palmer. The patients had 24-hour-ambulatory blood pressure measurements upon entering the study. Every 4 months they underwent optical coherence tomography to measure glaucomatous progression by thinning of the retinal nerve fiber layer (RNFL), along with IOP and systemic blood pressure measurements.

Pressure Drop, RNFL Thinning

RNFL thickness decreased by.5 µm a year for every 10 mm Hg drop in 24-hour MAP, Zhou reported. RNFL decreased by.36 µm a year for every 10 mm Hg reduction in systolic pressure and 0.46 µm for a similar decrease in diastolic pressure.

The study also found significant differences in RNFL progression between the highest and lowest fourths of each blood pressure metric, Zhou said. For average 24-hour mean arterial pressure, the difference between the lowest (81-90 mm Hg) and highest (94-99 mm Hg) groups was a 0.68-µm greater per year loss (P = .017). For minimum 24-hour diastolic blood pressure, the difference between the lowest (35-48 mm Hg) and highest (55-59 mm Hg) groups was a 0.63-µm greater per year loss.

The findings could indicate a need to achieve a balance between antihypertensive therapy and glaucoma risk, Zhou said, “but this must be approached cautiously.”

The study did not “manipulate” antihypertensive therapy, nor did it establish causation between such therapy and RNFL loss, he said.

“Management of systemic hypertension remains critical for cardiovascular health,” Zhou said. “However, in select patients, particularly those with glaucoma progression at low IOP and low 24-hour blood pressure, it may be reasonable to coordinate with primary care physicians or cardiologists to evaluate whether excessive nocturnal hypotension is occurring.”

Questions to Ask Patients

The findings add to earlier evidence suggesting antihypertensive therapies can complicate control of glaucoma, said Manjool Shah, MD, a glaucoma specialist at the W.K. Kellogg Eye Center at the University of Michigan in Ann Arbor, Michigan.

Ophthalmologists “give short shrift” to asking patients which blood pressure medicines they take and when they take them, and measuring blood pressure in the office and determining if it changes overnight.

“When I’m interrogating symptoms of low blood pressure, I try to ask: ‘Do you ever get up in the middle of the night to go to the bathroom and are you ever dizzy’” Shah said. “That might be a sign that your blood pressure is a little low while you’re asleep. Certainly, this should be on the differential diagnosis when you have an ostensibly well-controlled glaucoma patient who is nevertheless getting worse.”

Some of these patients might even go on to have invasive glaucoma surgery to preserve RNFL, he said. “All we might need to do is switch their blood pressure medicines around and they’d be fine,” Shah added.

The new study underscores the importance of improved communication between the ophthalmologists treating a patient’s glaucoma and internists and cardiologists prescribing antihypertension drugs.

“Hopefully this will be yet more evidence to bring those worlds a little closer together in an effort to do better for our patients,” Shah said.

This study was funded by Research to Prevent Blindness. Zhou and Shah reported having no relevant financial conflicts of interest.

Richard Mark Kirkner is a medical journalist based in Philadelphia.