Caffeine Transiently Reduces Retinochoroidal Microvascular Parameters

Caffeine consumption may transiently reduce several retinochoroidal microvascular parameters, according to research published in Photodiagnosis and Photodynamic Therapy. These changes, however, did not remain statistically significant after a 6-hour follow-up. 

Researchers enrolled 48 participants and randomly assigned them to consume a cup of coffee with caffeine (n=24; mean age, 23.45 years; 50% women) or without it (n=24; mean age, 22.73 years; 50% women). All participants underwent comprehensive examinations including intraocular pressure (IOP) measurement and slit lamp analysis. Investigators measured retinochoroidal microvascular parameters at baseline, 30 minutes, 1 hour, 6 hours, and 24 hours after coffee consumption via optical coherence tomography (OCT) and OCT-angiography (OCT-A). Participants assigned to the caffeine group consumed 2 grams of instant coffee mixed with 200 mL of water. 

Participants who consumed caffeinated coffee demonstrated decreases in parafoveal superficial capillary plexus (SCP) vessel density (baseline: 54.45%; 30 minutes: 51.8%; 1 hour: 51.92%), parafoveal deep capillary plexus (DCP) vessel density (baseline: 55.16%; 30 minutes: 52.45%; 1 hour 52.83%) outer retinal flow area (baseline: 8.87 mm²; 30 minutes: 8.03 mm²; 1 hour: 8.11 mm²), choriocapillary flow area (baseline: 20.95 mm²; 30 minutes: 19.82 mm²; 1 hour: 19.62 mm²), and subfoveal choroidal thickness (SFCT; baseline: 295.06 µm; 30 minutes: 277.08 µm; 1 hour: 260.71 µm).   

The caffeine’s effect did not remain statistically significant after 6 hours, and participants who consumed decaffeinated coffee did not experience significant changes in any microvascular parameters at any time point.  

“Caffeinated coffee consumption was found to be associated with significant changes in retinochoroidal microvascular morphology, including parafoveal SCP and DCP [vessel densities], outer retinal and choriocapillaris flow areas, as well as the SFCT,” according to the researchers. “Having said that, these slight and, most likely, transient changes are highly improbable to have clinical implications.”

Study limitations include a small sample size, the use of convenience sampling, and potential confounding due to differences in ingredients between caffeinated and decaffeinated coffee.