The buildup of fluid pressure inside the eye (intraocular pressure, or IOP) is the primary cause of optic nerve damage and consequent vision loss experienced by people with glaucoma. Studies have suggested that caffeine can affect IOP, but none had specifically explored the potential effects of caffeinated beverages on glaucoma risk. A team of investigators conducted a small study, published in the British Journal of Ophthalmology, that addressed this knowledge gap.*

What they did

The retrospective cross-sectional study involved respondents to the 2005-2006 National Health and Nutrition Examination Survey (NHANES), an annual survey of approximately 10,000 people in the U.S. conducted by the National Center for Health Statistics. The survey, designed to assess the health and nutrition status of American adults and children, includes:

• Interviews 
• Physical examinations 
• Blood samples

The 2005-2006 survey also contained glaucoma tests. Of the 1,678 respondents with recorded eye test results, 84 adults (5%) had glaucoma. These participants were asked how much and how often they had consumed each of the following beverages (caffeinated and decaffeinated) during the previous 12 months:

• Coffee 
• Hot tea
• Iced tea
• Soft drinks

Most (53.2%) of the participants were Non-Hispanic White, but the study was adjusted for ethnicity, as well as:

• Age
• Body mass index (BMI)
• Gender
• Smoking status
• Diabetes

What they found

Those who consumed at least one cup of caffeinated hot tea daily had 74% lower odds of having glaucoma than participants who did not drink a minimum of one cup of hot tea daily.

No statistically significant associations were found between reduced glaucoma risk and the consumption of

• Decaffeinated hot tea
• Decaffeinated iced tea
• Caffeinated or decaffeinated coffee
• Caffeinated or decaffeinated soft drinks

What it means

Although the reduced risk is sizeable within the context of the study, the generalizability of the results is limited by the study’s small size, retrospective observational design, and when the glaucoma diagnosis was received, as well as the absence of other data that could impact the results, including:

• Size of the cup that the beverage was in
• Type of tea consumed
• Length of time the tea was brewed

Many teas have been shown to contain antioxidants and possess anti-inflammatory and neuroprotective benefits. Since previous studies have indicated that oxidation and neurodegeneration may play a part in glaucoma risk, the new study results do merit further exploration through larger, prospective studies.

*Wu, C. M., Wu, A. M., Tseng, V. L., Yu, F., et al. (2018, Aug. 1). Frequency of a Diagnosis of Glaucoma in Individuals Who Consume Coffee, Tea and/or Soft Drinks. British Journal of Ophthalmology.  https://pubmed.ncbi.nlm.nih.gov/29242183/

Any sources from outside of Prevent Blindness do not imply an endorsement from Prevent Blindness. The contents of the material used are the responsibility of the authoring organization, Responsum Health.