In cockroach, there are two types of eyes, i.e., a pair of simple eye and a pair of compound eyes.
A compound eye has upto 2000 hexagonal units called ommatidia. These are responsible for producing mosaic vision. The adjacent ommatidia are separated internally by the pigment cells.
An ommatidium has two parts
(i) Outer dioptoric or focussing part, which consists of a corneal lens, two comeagen cells, a crystalline cone and four cone cells or vitrellae.
(ii) Inner receptive part has a spindle-shaped pigment containing rhadome surrounded by eight
retinulae which continue as nerve fibre.