Pigment Epithelium

The pigment epithelium lies on the inside of the retina of the eye and consists of a flat, single-layer epithelium. It is colored by the contained pigments, especially melanin black.

The pigment epithelium includes the photoreceptors that capture the light of the image passing through the lens. Its black colour also prevents light reflections in the eyeball.

https://de.wikipedia.org/wiki/Netzhaut#Retinales_Pigmentspithel_.28RPE.29 _{(Wikipedia CC-by-sa-3.0)}