Polarized light microscopy.

Polarized light is the light in which all the rays vibrate in one plane. A polarizing microscope has two disk accessories. They are made up of polarizing plastic that allows light vibrating in one plane to pass. One of them is called a polarizer (placed below the condenser). Another similar disc is placed in the top part of the microscope and cuts off all the light vibrating in a perpendicular plane. This disc is called analyzer. The placement of the discs is such that they allow light vibrating in planes perpendicular to each other. Hence when both the Figure 1: Principle of polarizing microscopy disks are in place no light can pass on to the eyepieces. Hence through the eyepieces only dark background is seen unless Foreign body (ies) a doubly refractile object is placed in the path of polarized On polariscopic examination different foreign bodies have light, in which case, the doubly refractile object appears characteristic appearance. They can be found amidst foreign illuminated against a dark background [Figure 1]. body granulomas (both allergic and non-allergic type) and most commonly within the multinucleated giant cells. Usually organic and inorganic substances with rigid yet Various foreign bodies can be identified on the basis of repeatable structure like crystals, sand, talc, wood, amyloid and other fibrillary structures are seen on polarized light microscopy. Certain foreign bodies can be detected on routine hematoxylin and eosin staining (H and E) while special stains are required for metabolic or deposition disorders.