https://pubmed.ncbi.nlm.nih.gov/12357387
This article suggests, 'kavain impairs vascular smooth muscle contraction, likely through inhibition of Ca(++) channels.'
My take is kava is neither a strong vascular consttictor or dilator, it leans more towards dilation [vessel widening] which, in my experience keeps us warm and promotes healthy blood & water circulation.
By feeling you mentioned, ocular sensitivity increases, maybe that is eye vein contraction. Bula.