A trip to the out of hours doctor service + a three week old baby + one right eye swollen shut = Eye drops of joy.
Three week old babies might not be able to do much, but they can sure clamp their eyes shut.
Worry not, a fantastic internetty type lady gave me the tip of putting the drop on the corner of the eye so when it opens the drop slides in. If only I had known about this with my two previous children. All that time wasted growling, 'will you open your flipping eye!'