These two phrases mean basically the same thing. Alternate translation: "I will lead the blind in paths that they do not know" (See: [[rc://en/ta/man/jit/figs-parallelism]])
Yahweh speaks of his people being helpless as if they could not see because they walked in darkness, and of his helping them as if he caused light to shine in the darkness. (See: [[rc://en/ta/man/jit/figs-metaphor]])