These are painful days for Dale Chihuly, as he winds down a long career facing a challenge that stabs at the heart of any artist: his originality. Mr. Chihuly emblazoned his signature on the world by working and rethinking the vocabulary of glass as art. Physical challenges and scars compounded the difficulty of that path. He lost vision in an eye in a 1976 car crash that also permanently injured an ankle and a foot. A shoulder injury from a bodysurfing accident made glass blowing, with its heavy weights of pipes and glass, impossible to do. He suffers from bipolar disorder, marked by sweeping swings of elation and depression. And with greater dependence on others, he said, has come greater vulnerability to claims that his work is not his own.