Agreed, the sea creatures have evolved to capture even more light. I'm only guessing, but I would think the pressure and temperature sensors on fish would be more important than sight?
You mean, sensors to detect at a distance? For temperature, most deep-sea creatures have large amounts of insulation to survive the cold & thus would be difficult to detect (especially since water is also an insulator). For pressure, those exist and are called tendrils/antennae.
