My windscreen wipers on my vauxhall zafira not working completely?

My windscreen wipers for some reason have started to not clean as much of the screen as they did before. They seem to be stopping short of going completely from one side to the other..So now they stop at the right of the screen (looking from drivers seat) about 4 inches from the edge of the window when going from bottom upwards. This is very annoying as it is not cleaning the last part of the windscreen...Can the wipers be adjusted.?