Physiologically, microglial cells (resident macrophages) are present only in the inner retina. The subretinal space, located between the retinal pigment epithelium (RPE) and the photoreceptor outer segments (POS), is devoid of all mononuclear phagocytes and form a zone of immune privilege. In AMD, several studies showed a strong association between subretinal mononuclear phagocytes infiltration and advanced forms of AMD. Experimental work in mice suggest that this infiltration plays an important role in the pathogenesis of this condition by producing inflammatory cytokines.