The writer speaks of eyes that cannot see well as if they were darkened. This can be stated in active form. Alternate translation: "Please make them unable to see anything" (See: [[rc://en/ta/man/jit/figs-metaphor]] and [[rc://en/ta/man/jit/figs-activepassive]])
Weak backs are spoken of as if they are shaking in weakness. Alternate translation: "cause their backs to be too weak for them to do anything" (See: [[rc://en/ta/man/jit/figs-metaphor]])