RESULTS	However , in the subgroup of patients with initial light perception-only vision , VIT produced a threefold increase in the frequency of achieving 20/40 or better acuity ( 33 % vs 11 % ) , approximately a twofold chance of achieving 20/100 or better acuity ( 56 % vs 30 % ) , and a 50 % decrease in the frequency of severe visual loss ( 20 % vs 47 % ) over TAP .\