What are considered the most common glial cells in the retina?

• A. Astrocytes
• B. Microglia
• C. Muller cells
• D. Ependymal cells

Answer: (C)

Glial support in the retina is dominated by Müller cells, which are the most common glial type there. These elegant radial cells span nearly the whole thickness of the retina, from the inner limiting membrane to the outer limiting membrane, and wrap around neurons in each layer. Because of this extensive presence, Müller cells provide essential scaffolding and metabolic support to all retinal neurons, helping to maintain ion and water balance, recycle neurotransmitters, and support the blood-retinal barrier. They also play a role in the retina’s optical properties by guiding light through the neural tissue and reducing scattering. While astrocytes are present, especially near vessels and in the nerve fiber layer, and microglia exist as resident immune cells in smaller numbers, they do not match Müller cells in abundance. Ependymal cells line the brain’s ventricles and aren’t a feature of retinal tissue.