Sea urchins are mobile pincushions. Their spiny defense system dominates their appearance. They have no eyes per se. Instead, a sea urchin is an eye: a very prickly one.
The tube feet that propel urchins possess opsins, which are the proteins that make animal eyes possible. Opsins at the base of the tube feet are complimented by a 2nd set of opsins scattered over an urchin’s surface.
Altogether, an urchin’s mind has enough pixelated information to put together a rough image: good enough to tell light from dark and detect movement; sufficient sight to know when to put one’s spines up or run for cover.
Sea urchins have no brain. They do have a simple nervous system that rings their mouth: right where the action is.