I think it was in "Writing Excuses" that someone said this: "If a scene doesn't advance the plot, help develop a character or worldbuild, it is essentially useless." I would also claim that this goes for sentences as well, with the added clause of, "if it doesn't help establish a scene(background, character's emotions), the sentence is useless."
Someone also said that "you'll always want to have your sentences do more than one thing at once". Basically, your description could also be character building at the same time, if done correctly. For example, the line, "the chasm in the ground looked like an unsutured wound" would convey that the main character knows something about being a doctor. Maybe. coughs That was also a blatant reference to a certain series, heh... XD