1. examination by means of a diascope.

How do you do diascopy?

Diascopy involves applying pressure to the skin either by pressing it apart between the thumb and index finger or by applying a glass or plastic slide over the involved skin surface. Hyperemic areas blanch with diascopy, but purpuric lesions do not.

What is diascopy used for?

Diascopy is used to determine whether erythema in a lesion is due to blood within superficial vessels (inflammatory or vascular lesions) or is due to hemorrhage (petechiae or purpura). A microscope slide is pressed against a lesion (diascopy) to see whether it blanches.