Microglia, the innate immune cells of the retina, can actively monitor changes in the surrounding microenvironment.Photoreceptors, as the primary neurons of the retina, can convert light signals into electrical signals.Microglia play an important role in the function or survival of photoreceptors in various physiological and pathological conditions of the retina.During the development of the retina, microglia phagocytize cell debris and promote neurogenesis and synaptic plasticity.In a healthy retinal environment, microglia can maintain retinal homeostasis, maintain synaptic structure and function of neurons, and secrete neurotrophic factors.In the past, more attention has been paid to the damage of microglia in retinal diseases.In acute retinal injury and stress (retinal detachment, prion-induced damage, light-induced damage), the protective effect of microglial cells on photoreceptors is greater than damage.In retinal chronic inflammatory diseases such as retinitis pigmentosa, age-related macular degeneration and diabetic retinopathy, the immune microenvironment is imbalanced, microglia are over-activated, release a large number of inflammatory factors, phagocytize non-apoptotic photoreceptors, the damage is greater than protective effect.How to utilize the protective effect of microglia and inhibit their damage is of great significance for the treatment of retinal diseases, especially chronic inflammatory diseases.This article reviews the effects of microglia on photoreceptor cells under different retinal conditions.

Microglia; Photoreceptor; Retina; Retinal diseases