Three basic types of glial cell are found in the retina, Müller cells, microglia and astroglia.
Müller cells are the major glial element of the retina. Muller cell bodies are located in the inner nuclear layer and project irregularly thick and thin processes from the internal limiting membrane to the bases of the rods and cones where they form a row of junctional complexes called the outer limiting membrane. They form architectural support structures, provide metabolic support to retina, play a central role in the homeostatic regulation of the retina and maintain low synaptic levels of neurotransmitters. Also, following injury to the retina, it has been shown that Müller cells actually de-differentiate into a neural progenitor. Recently published research has shown that Müller cells are living optical fibers in the vertebrate retina acting as light conductor which funnels light to the rods and cone cells.
Microglia are phagocytic cells in the retina required for neuronal homeostasis and innate immune defense. The immunological potentialof microglia is comparable with blood monocytes. and macrophages.