This time, Michael Mosley reveals a new discovery that could help us all improve our eyesight and Dr Chris van Tulleken carries out an experiment with the University of Worcester to find out whether the fad for going gluten free can be good for us. Surgeon Gabriel Weston witnesses a breakthrough that could cure rheumatoid arthritis and other autoimmune diseases and Dr Saleyha Ahsan investigates the signs and symptoms of depression - what should we all look out for?