Eating leafy greens may benefit people with glaucoma, Dr. Ou found. These plants are a source of dietary nitrate. One study showed that the effect was greatest in glaucoma patients with early paracentral visual field loss at diagnosis associated with vascular dysregulation.
How much is enough? In another study, patients who ate one serving a week or more of collard greens or kale had lower glaucoma risk compared to those who had less than a serving a month.
Most of the research is on glaucoma risk rather than glaucoma progression. “I do tell patients to eat green leafy vegetables because there can’t be too much downside to that,” said Dr. Ou.
As for coffee, there is evidence both pros and cons for glaucoma. In one prospective, randomized controlled trial, 106 subjects ingested about 8 ounces of either caffeinated or decaffeinated coffee. The caffeinated coffee appeared to increase IOP about 1 mm Hg, but increase ocular perfusion pressure by about 1.25 mm Hg to 1.5 mm Hg.
“Those two counteracting forces likely mean that drinking a cup of coffee is not going to make a huge difference,” said Dr. Ou. At least one animal study suggests that caffeine could protect against ganglion cell loss. “I generally tell patients a cup is not a problem.”
In the landmark SPRINT trial, people with hypertension whose systolic blood pressure was lowered to 120 mm Hg or lower had a one-third reduced risk of cardiovascular disease and almost a one-quarter reduced risk of death compared to people whose systolic pressure was lowered to 140 mm Hg.
“So huge benefits,” said Dr. Ou. While the rates of serious adverse events were not statistically different between the 2 groups, there was a higher rate of hypotension and syncope in the intensively treated group.
“Of course, this is an issue for our glaucoma patients because we know that ocular perfusion pressure is likely playing an important role, though that is not entirely well defined at this point,” said Dr. Ou.
A follow-up study showed that the cardiovascular and mortality benefits held for patients 75 years old or older, said Dr. Ou. But in this group, the mean diastolic pressure in the intensive group was 62 mm Hg, which was 5 mm Hg lower than the standard group, raising questions about ocular perfusion. The Early Manifest Glaucoma trial showed that a systolic pressure lower than 125 mm Hg was a predictor of long-term progression in glaucoma.
Armed with this information, Dr. Ou asks patients what cardiovascular risk factors they have. If they do not have many or if glaucoma is progressing despite IOP control, she insures that they are not being overtreated for hypertension.
On the other hand, if patients have low baseline blood pressure, she may talk to them about easy things they can do to boost their ocular perfusion pressure.