To explore ocular changes in healthy people after caffeine consumption.
This prospective observational study was carried out with students of the Turgut Özal University Medical Faculty from May 15 to 15 December 2014. Enrolled in the study were 17 healthy subjects (n = 17 eyes), with a median age of 24 (IQR 1), ranging between 21 and 26 years. The control group (6 females, 11 males) aged between 23 and 28 (median 25 years [IQR 4.75]). For study, one eye from each participant was randomly selected. To obviate the effect of diurnal variations, tests were performed at the same time of the day (10:00 a.m.-12:00 p.m.). Each subject was given an ophthalmologic examination before the study to exclude those with undiagnosed ocular disease. Version 6.0 Cirrus high-definition optical coherence tomography (HD-OCT) (Carl Zeiss Meditec, Dublin, CA) was used to measure CT at the fovea, and 1500 μm nasal and 1500 μm temporal to the fovea. After baseline OCT measurements, participants were asked to have 200 mg oral caffeine intake or a placebo capsule (200 mg lactose powder). Two further OCT measurements were applied at the first and fourth hours of caffeine intake. All participants also had intraocular pressure (IOP) and ocular pulse amplitude (OPA) measurements recorded before, first and fourth hours of caffeine intake. IOP and OPA were measured using the dynamic contour tonometry (DCT) (Swiss Micro Technology AG, Port, Switzerland).
The groups showed no significant difference by means of age, gender, spherical refraction and axial length (p > 0.05). Baseline choroidal thickness measurements of the study and control group showed no significant difference. Oral caffeine intake caused a significant reduction in choroidal thickness compared with baseline, at all three measurement points, (p < 0.05). There were no significant changes in IOP and OPA measurements compared with the baseline values (p > 0.05). The choroidal thickness still continued to decrease for at least 4 h following caffeine intake; whereas, the difference between 1 and 4 h was not statistically significant (p > 0.05). However, choroidal thicknesses, IOP and OPA values of the control group revealed no significant difference at all points when comparing measurements at baseline with 1 and 4 h after placebo intake (p > 0.05).
We found no significant change in IOP and OPA following oral 200 mg caffeine intake, while CT significantly decreased, for at least 4 h.