capillaroscopy

noun

cap·​il·​la·​ros·​co·​py ˌkap-ə-lə-ˈräs-kə-pē 

variants also capillarioscopy

-ˌler-ē-ˈäs- 

plural capillaroscopies also capillarioscopies

: diagnostic examination of capillaries, especially of the nail beds, with a microscope