ommatidium One of the individual, light-sensitive units that together form a compound eye. Each ommatidium consists of a cuticular lens below which is the crystalline cone. Below this are six or seven elongated retinula cells, which have close-packed microvilli towards the centre forming a structure called the rhabdome. Pigment cells surround the retinula cells. See also EYE.

ommatidium (pl. ommatidia) See compound eye.