I was reading the question about shapeshifters' nervous systems.
And I figured, the eyes and ears being merely for appearance sake, that would imply that each cell in the shape-shifter's body is either capable of, or an equal and continuous part of their sensory input.
This would imply that Odo either has the ability to have eyes on his back (without the appearance of eyes in his back), or is made up of trillions of eyes and ears coming together to create a composite image of his surroundings.
However, I tend to remember that Odo was infrequently caught off guard in the series, and can't remember any occurrence of Odo showing superior senses.
Is this a plot hole?
Is there some in-universe explanation for the limitations to his sight/hearing/...?