Actor William Hurt's ophthalmologist testified Thursday at a palimony trial in state Supreme Court in Manhattan that she knew the Oscar winner was not married to former ballerina Sandra Jennings, but she was unable to explain why medical records identifying Jennings as his "spouse" in 1983 were later altered. "I know they were not married when they had the baby," testified Dr. Barbara Barker, who is also Hurt's personal friend. Asked by Jennings' attorney how she knew that, Barker responded, "Because he never called her 'my wife.' " Jennings, the mother of Hurt's 6-year-old son, is trying to prove she had a common-law marriage and is seeking half of Hurt's estimated $10-million earnings. Earlier, Hurt had testified that in August 1983 he wrote Jennings' name on a medical form in a box entitled "Spouse-Head of Household" because he considered her the head of the household. On the same form, in a box entitled "Marital Status," he wrote "mated." Barker was shown conflicting copies of a billing ledger, one with "Spouse: Sandra Jennings" at the top, but those words were deleted with white-out fluid on another copy. She testified that she did not know who altered the document. In other testimony, the child's former nanny, Linda Patrick of Brooklyn, said the actor once asked her, "How do you like working with my wife?' I said, 'Sandy? She seems to be a very nice person.' " The trial, in its fourth day, was adjourned until Monday morning.