The effect of caffeine on choroidal thickness in young healthy subjects.

BACKGROUND To investigate the effect of oral caffeine intake on choroidal thickness using optical coherence tomography (OCT). METHODS Eighteen otherwise healthy caffeine users and 18 controls were enrolled. All participants underwent OCT scanning with high-speed and resolution spectral-domain OCT device (3D OCT 2000, Topcon, Japan) at baseline, and 1 and 3 h following 200-mg oral caffeine intake in the study and after oral placebo in the control group. The measurements were taken in the morning (10-12 am) to avoid diurnal fluctuation. RESULTS The median choroidal thickness at the fovea prior to oral caffeine intake was 337.00 (IQR 83.75) μm, which decreased to 311.00 (IQR 79.25) μm at 1 h and 311.00 (IQR 75.00) μm at 3 h following oral caffeine intake (p = 0.001, 0.002, respectively). The median choroidal thickness was also significantly decreased following oral caffeine intake at other five extrafoveal points (p < 0.05 for all). The difference in choroidal thickness was not statistically significant between 1 and 3 h of caffeine intake at all six points. In the control group, the median baseline choroidal thickness at the fovea was 330.00 (IQR 88.75) μm, which was 330.50 (IQR 80.75) μm at 1 h and 330.50 (IQR 90.75) μm at 3 h (p = 0.552, 0.704, respectively). CONCLUSIONS Caffeine causes a significant decrease in choroidal thickness following oral intake. This decrease might be a result of reduced ocular blood flow due to its vasoconstrictive effect.