[falsedan]

  > searchlights or even lasers

Think about the return on investment on these: how much energy to grow and power vs. the improved food gathering. Also: would this make the creatures easier to find by predators?

Galagos developed large eyes rather than sonar, true. I refer you to my other comment:

  > Perhaps eyes convey a general advantage, regardless of how you find food?

[logicallee]

I think we can all agree that my point is made, and it's easy to imagine sentient extraterrestrials without photoreceptors.