11. 75- year-old farmer visited general practitioner with weakness, diarrhoea, decreased vision, and purulent discharge from eyes. On examination, there were subcutaneous haemorrhage in the arms and legs. Eyes showed marked inflammation and dilatation of conjunctiva vessels and margins of eyelid, fissure at the angle of the mouth, tongue was sore and swollen. Deep tendon reflexes were diminished. Which vitamin deficiency causes changes in the eye?