Caffeine raises IOP in POAG

Coffee can push eye pressure up — at least for a while — in people with primary open-angle glaucoma. That is the basic takeaway from a randomized crossover trial that keeps getting resurfaced because it answers a very practical clinic question. If a glaucoma patient shows up with a higher-than-expected intraocular pressure reading, recent caffeine intake may be one reason. But the catch is that the measured bump looked statistically real while still being small enough that the authors did not think one cup, by itself, was likely to change care. ### What exactly was tested? The study looked at one cup of caffeinated coffee containing 182 mg of caffeine in 106 people spread across several groups — high-tension primary open-angle glaucoma, normal-tension glaucoma, glaucoma suspects, ocular hypertension, and healthy volunteers. It used a prospective, double-masked, randomized crossover design, which is a solid way to test a short-term effect because each participant can be compared against a control condition. ### What changed after the coffee? The short version is that intraocular pressure, or IOP, went up after the caffeinated drink, and ocular perfusion pressure, or OPP, also rose. The ophthalmology trade write-up focused on the glaucoma angle — especially patients with primary open-angle glaucoma — because that is the group where even small pressure shifts get attention. The trial paper’s own conclusion was more clinically important after a single cup. ### Why does IOP matter so much? IOP is the pressure inside the eye. In glaucoma, that pressure is one of the main modifiable risk factors for optic nerve damage. So even a modest temporary rise matters conceptually. A clinic visit is basically a snapshot, not a movie. If caffeine can tilt that snapshot upward, a doctor could be looking at a transient blip rather than a true worsening trend. ### What is ocular perfusion pressure? OPP is a rough way of thinking about the blood-pressure side of eye circulation relative to eye pressure. Lower OPP has often been the bigger glaucoma worry, because reduced perfusion may mean less blood flow to the optic nerve. That is why this result is a little counterintuitive at first glance — the coffee raised both IOP and OPP, not just IOP. So this was not a simple story of “coffee worsens every glaucoma-related variable.” ### Does this mean glaucoma patients should quit coffee? Not really. The paper did not say that one cup meaningfully harms patients, and it definitely did not show that coffee causes glaucoma progression from a single exposure. Broader research is more mixed. One large study found no overall association between total caffeine intake and developing primary open-angle glaucoma, though some subgroup analyses hinted at susceptibility. ### Why might the effect vary person to person? Tolerance seems to matter. Later work in healthy people suggested caffeine’s effect on IOP and OPP can differ between low- and high-caffeine consumers, which fits common sense — the body adapts. So the patient who rarely drinks coffee may not respond like the patient who lives on it. That makes blanket rules less useful than simply asking what someone had before the visit. ### So what should clinicians do with this? Mostly, use it as context. If a pressure reading looks unexpectedly high, recent caffeine is one possible confounder worth documenting before jumping straight to more drops, laser, or surgery. That is not an excuse to ignore a high reading — just a reminder that glaucoma management works best off repeated measurements and patterns, not one number taken after a coffee run. ### Bottom line? One caffeinated coffee can briefly raise measured eye pressure in people with or at risk for primary open-angle glaucoma. Basically, it is a triage clue, not a panic signal.