Interphotoreceptor matrix proteoglycan-2 (IMPG2) is part of an extracellular complex occupying the interface between photoreceptors and the retinal pigment epithelium in th e fundus of the eye.Interphotoreceptor matrix proteoglycan-2 is part of an extracellular complex occupying the interface between photoreceptors and the retinal pigment epithelium in the fundus of the eye.[supplied by OMIM].