Effects of caffeine intake on the biomechanical properties of the cornea: a placebo-controlled, double-blind, crossover pilot study in low caffeine consumers

Purpose To assess the short-term effects of caffeine intake on the biomechanical properties of the cornea, as well as its possible association with the intraocular pressure (IOP), as measured by corneal visualization Scheimpflug technology (CorVis ST) in healthy subjects. Methods Twenty-two low caffeine consumers ingested either a caffeine (4 mg/Kg) or placebo capsule in two separate sessions. IOP and corneal biomechanics parameters, including time, velocity, length, and deformation amplitude at the first applanation (A1T, A1V, A1L, and A1D, respectively); time, velocity, length, and deformation amplitude at the second applanation (A2T, A2V, A2L, and A2D, respectively); time at the highest concavity (HCT), radius curvature at the highest concavity (HCR), deformation amplitude at the highest concavity (HCDA), and peak distance (PD), were measured with the Corvis ST before and after 30 min, 60 min, and 90 min of caffeine/placebo intake. Results Caffeine intake reduced the corneal deformability, inducing significant changes in A1T, A2V, A2T, HCDA, HCT, and PD (allpvalues < 0.05). Non-corrected and biomechanically corrected IOP values were higher after caffeine intake (p = 0.001 and 0.033, respectively). Also, the changes in IOP after caffeine intake were positively associated with A1T (r = 0.790 to 0.962), and negatively associated with A2T (r = - 0.230 to - 0.722) and PD (r = - 0.506 to - 0.644). Conclusions Caffeine intake reduces the corneal deformability, with these changes being partially associated with the IOP rise. These findings evidence that exogenous factors such as caffeine intake should be taken into consideration when making clinical decisions that are based on the biomechanical properties of the cornea.