retinula
/rɪˈtɪnjʊlə/Zoology
noun
In the eyes of various invertebrates: a group of elongated neuronal cells forming the light-sensitive unit of the retina (or of each ommatidium in a compound eye). Frequently attributive, especially in retinula cell.
Origin
Late 19th century; earliest use found in Francis Bell (1855–1924). From German Retinula from Retina + -ula.