In April 2019 researchers from Saudi Arabia published the results of their study to assess the effect of a single dose of green tea on the quality and quantity of tears in individuals with normal eyes. A total of 40 individuals (22 men, 18 women; age 19-39 years) were asked to consume a single serving of green tea, whilst a further 40 individuals (20 men, 20 women) were matched for age and acted as a control group for comparison. Information on dry eye symptoms was collected via a questionnaire. Eyes were examined using a slit lamp and a phenol red thread test performed on both eyes. In addition a tear sample was collected 30 minutes before and 60 minutes after drinking the green tea. Results showed that the phenol red thread test measurement was lower and the average tear ferning grade significantly higher after the green tea consumption when compared to before consumption. An analysis revealed that the tear ferning grades increased in 97.5% of individuals whilst the red phenol thread scores decreased in 80% following the green tea consumption. The researchers therefore concluded that drinking green tea could have a significant effect on the eye tear film quality, with the tear quality appearing to decrease after green tea consumption.
Masmali AM et al. The acute effect of a single dose of green tea on the quality and quantity of tears in normal eye subjects. Clin Ophthalmol. 2019 Apr 10;13:605-610