The point is that the other philosophers, typified by Plato with his cave, allege that the senses "lie" to you and that they are therefore unreliable sources of information about how to live.
I'm terribly near-sighted, and I like to use the example of eyesight.
Without glasses, everything is dangerously blurry: precisely as it should appear to someone with an elongated eyeball. If I saw the world "as it really is" (i.e. "not blurry"), then my senses would be lying to me, leading me to believe that my eyeball is round. But it doesn't, because it isn't.
Evaluating sensory data is like asking a toddler a question about your physical appearance: the toddler doesn't know how to manage that delicate, social interaction; they will probably blurt out the first, unfiltered impression they have, without any thought as to the implications.
There is also a strong contrast here, not only against Plato, but also, against Democritus. Both philosophers would have seen near-sightedness as evidence that the senses are unreliable, and that the objects of perception are just illusions that come from a more fundamental reality.