From the literature on the Net, we see that VITAMIN B2 (riboflavin) and VITAMIN B3 (niacin) may improve vision in cataract patients, sometimes within a few days.
But please note: There are also warnings that taking more than 10mg of Vitamin B2 per day may make vision worse. This is because Vitamin B2 (the yellow B vitamin) also has a 'photosensitizing effect', generating ROS (free radicals) upon exposure to blue light that would worsen cataract symptoms. What can we do to get the benefits of B2 without the disadvantages? I am just guessing - but maybe, if we invest in a pair of good eyeglasses with blue-blocking lenses, then, we would get less exposure to blue light and hence, we could then take more Vitamin B2 for its cataract reversal properties - up to 50mg per day - and get an improvement in vision. For the moment, I cannot afford blue-blocker eyeglasses and so I cannot test this out. Therefore, I am restricting intake of Vitamin B2 supplements to 10mg/day.
As for Vitamin B3 (niacin), I recommend getting it from food rather than supplements, which can have side-effects. I think we can get enough of it by consuming kale.