Caffeine shown to cause retinal vessel constriction

Retinal vessels in young healthy individuals appear significantly constricted an hour after consumption of caffeine.

A study in this month's Acta Ophthalmologica looked at retinal vessel diameter in 17 healthy individuals before and after consumption of 200mg oral caffeine. Average constriction was 6 microns in arterioles and 10 microns in venules, both of which were statistically significant.

The authors suggested the constriction was part of the autoregulation response of retinal vessels, which maintain constancy of blood flow in the healthy retina in response to cardiovascular changes. The findings may have clinical implications in cases where vessel changes are being assessed.