Recently, researchers first documented visually guided behaviour in starfish:
A study has shown for the first time that starfish use primitive eyes at the tip of their arms to visually navigate their environment. Research headed by Dr. Anders Garm at the Marine Biological Section of the University of Copenhagen in Denmark, showed that starfish eyes are image-forming and could be an essential stage in eye evolution.
The researchers removed starfish with and without eyes from their food rich habitat, the coral reef, and placed them on the sand bottom one metre away, where they would starve. They monitored the starfishes’ behaviour from the surface and found that while starfish with intact eyes head towards the direction of the reef, starfish without eyes walk randomly.
They think that their find may help us understand the evolution of eyes because the starfish eyes (at the tips of the tentacles), which lack true optics, are close to the theoretical “eye” of early evolution, and how they are used today might determine the earliest tasks that eyes were used for.
Maybe. The problem is, what starfish use tentacle eyes for today may or may not be the tasks that the earliest sighted organisms used their eyes for. Maybe soft fossils will shed some light down the road.