Müller cells are the principal supporting glial cells of the retina and are considered analogous to central nervous system radial glial or ependymal cells. They have a radial orientation and extend through the depths of the retina from the inner surface, where their expanded ‘foot process’ lies adjacent to the inner limiting membrane, to their outer limit where they have adherens junctions with photoreceptor inner segments to form the external limiting membrane. They envelop blood vessels, neuronal cell bodies and processes, creating glial ‘tunnels’ via a series of cytoplasmic processes.