The effect of caffeine on tear secretion.

Purpose: Caffeine, probably the most widely consumed psychoactive substance, is claimed to have conflicting effects on some tear film dynamics. This study sought to investigate the effect of orally ingested caffeine on tear secretion.

Methods: In an examiner-masked, placebo-controlled, crossover experimental model, the effect of caffeine intake on tear secretion was studied in 41 healthy volunteers aged 20 to 26 years (mean, 23.0 ± 2.1 years). Participants were randomly assigned into two groups, A and B, to receive two different treatments in two sessions. Subjects in group A were exposed to 5.0 mg/kg body weight of caffeine dissolved in 200 mL of water on their first visit, whereas those in group B were exposed to 200 mL of water. On the second visit, however, the order of treatment was reversed. Schirmer 1 scores were measured repeatedly at 45, 90, 135, and 180 minutes after treatment. The baseline Schirmer 1 scores were compared with posttreatment scores.

Results: Schirmer 1 scores increased after caffeine intake. The increase was statistically significant at 45 and 90 minutes (p < 0.05) after caffeine intake. Age, body mass, and blood pressure had no correlation with Schirmer 1 scores (Spearman correlation test, p > 0.05). There was no influence of gender in caffeine's effect on tear secretion (F = 0.994, p = 0.399).

Conclusions: From our study, orally ingested caffeine appears to stimulate tear secretion in healthy non-dry eye subjects.