Effect of caffeine on superficial retinal vasculature of the macula in high myopes using optical coherence tomography angiography – A pilot study

Purpose: To monitor effect of caffeine on vasculature of the inner retina of high myopes Methods: This was a crossover, self‐control, randomized trial. Healthy young high myopes were recruited to take 200 mg of caffeine capsule and placebo capsule, randomly assigned in two visits separated by at least one week. Superficial retinal vasculature in terms of vessel length density (VD) and perfusion area density (PD) was captured and monitored using a spectral domain optical coherence tomography angiography (OCTA) machine. After baseline measurements, blood pressure (BP), intraocular pressure (IOP), and subfoveal choroidal thickness (ChT) were also monitored at 30‐min intervals till 3 h. Results: Eighteen subjects (6 male, 24.3 ± 3.1 years) completed the study. After taking the caffeine capsule, there was a significant increase in BP (p < 0.01), and reduction in ChT (p < 0.01), with no change in IOP (p = 0.36). VD demonstrated a trend of reduction at the central 1‐mm circle, and 1‐3 mm annulus (p < 0.01) following the ETDRS grid. Reduction trend of PD appeared at the central 1‐mm circle, 1‐3 mm annulus, and the entire 3‐mm circle (p < 0.01). Compared with baseline, VD and PD reductions were significant 180 min after taking the caffeine capsule at the central 1‐mm circle, but the reduction was small (VD: by 1mm ^-1; PD: by 1%). Changes in other regions were not significant. Conclusions: The current study found significant reduction in VD and PD after taking 200 mg of caffeine capsule. Such a small amount of alteration may be clinically irrelevant.