Sadly, Monet also developed cataracts as he aged. However when he first encountered the works of Turner and changed his own work significantly to reflect his influence, Monet's eyesight was still fine. His eyesight only declined after his most famous works were completed. Interestingly, his paintings post-cataract tended to be harsher in contrast, with more red-brown, and with sparser brushstrokes.

I've no idea how Turner's cataracts affected his work.