Caffeine, Coffee, and Tea: How Do They Impact Eye Pressure?

This audio article is from VisualFieldTest.com.Read the full article here: https://visualfieldtest.com/en/caffeine-coffee-and-tea-how-do-they-impact-eye-pressureTest your visual field online: https://visualfieldtest.comExcerpt:Caffeine, Coffee, and Tea: How Do They Impact Eye Pressure?Caffeine is one of the most widely consumed substances worldwide, found in coffee, tea, energy drinks and many soft drinks. Eye care patients often wonder if their morning coffee or tea could raise their intraocular pressure (IOP) or affect ocular blood flow. In general, a moderate dose of caffeine – roughly the amount in one or two cups of coffee (≈150–200 mg) – causes a small, temporary rise in IOP that peaks within about an hour of ingestion () (). In healthy eyes this increase is usually only ~1 mmHg and is clinically negligible () (). However, in glaucoma patients and ocular-hypertension cases, similar doses can raise IOP by ~3–4 mmHg above baseline (). Caffeine also slightly raises systemic blood pressure, so calculated ocular perfusion pressure (OPP) often increases by ~1–2 mmHg after coffee (). Paradoxically, despite higher OPP, caffeine’s vasoconstrictive effects tend to decrease small-vessel blood flow in the eye () (). Below we review the acute and chronic effects of caffeine on IOP and ocular perfusion, contrast coffee with tea (especially green tea catechins), and give practical advice for patients with high eye pressure.Acute Effects of Caffeine on IOP and Ocular PerfusionAfter drinking coffee or another caffeinated drink, caffeine is rapidly absorbed – reaching peak blood levels in about 1–1.5 hours (). At doses of roughly 150–200 mg (about one strong 8-oz cup of coffee), studies show a modest IOP rise. For example, a randomized trial found that drinking 182 mg of caffeine in coffee produced an average IOP increase of only ~1 mmHg at 60–90 minutes versus decaffeinated coffee (). In most people this change is statistically significant but trivial clinically () (). By contrast, a crossover study of glaucoma and ocular-hypertension patients reported that the same 180 mg dose raised IOP by about 3–4 mmHg at 60 minutes, whereas decaffeinated coffee (just 3.6 mg caffeine) caused almost no rise (). Thus, healthy individuals typically see <1 mmHg rise, while glaucoma suspects or patients can experience larger spikes after a normal cup of coffee () (). These caffeine-induced elevations generally begin within 30–60 minutes and tend to subside over a few hours as the caffeine is metabolized (half-life ~3–7 hours) ().Along with IOP, caffeine also slightly elevates ocular perfusion pressure (OPP) because it raises blood pressure. In one study 182 mg of caffeine increased calculated OPP by ~1.5 mmHg (at 60 min) compared to decaf (). In other words, eye driving pressure goes up slightly. However, multiple experiments show caffeine’s net effect is vascular constriction in the eye. A classic study observed a ~13% drop in macular blood flow one hour after 200 mg of caffeine (). Newer imaging confirms that even 100–200 mg doses cause meaningful reductions in ocular microcirculation () (). For example, optical-coherence angiography (OCT-A) scans after coffee show significantly narrowed retinal vessels and lower capillary blood flow, despite any OPP increase () (). One recent trial with 72 mg caffeine (a moderate coffee) found retinal capillary perfusion decreased by 2 hours, while larger-vessel retina/choroid flow actually rose (). Taken together, caffeine briefly raises driving pressure in the eye but constricts the ocular microvasculature, leading to reduced tissue perfusion () (). In summary, acute caffeine intake (e.g. one coffee) typically causes: a small, transient IOP rise (on the order of 1–3 mmHg) with peak effect ~1 hour Support the show