Birefringent Crystals Birefringent Crystals Birefringent literally means splitting a ray of light in two. Crystals bend light and become visible in joint fluid when viewed through a microscope with crossed polarizing filters. These crystals are also distinguishable by their shape and size. Urate crystals are needle-shaped and are about the size of a leukocyte.
Calcium pyrophosphate dihydrate crystals are smaller and are rhomboid-shaped.