Recent research has thrown considerable doubt on the claim that King George III suffered from variegate porphyria, but indicates that he suffered recurrent attacks of mania as part of his bipolar disorder. George III's last episode of ill health occurred during the final decade of his life (1810-20). This has been diagnosed as chronic mania with an element of dementia. During this period the king was blind and possibly deaf, which may have contributed to his psychiatric condition. His blindness was due to bilateral cataracts; serious consideration was given at the time to surgery, but this was not carried out. The possible contribution of the king's blindness to his illness is discussed with respect to the roles of his medical attendants. It was also claimed that George III showed progressive deafness and this claim has been re-examined. However, the medical reports by the attending physicians and psychiatrists (mad doctors) do not support this claim.