In the end Ms. Duke found contentment in an enduring fourth marriage; the presidency of the Screen Actors Guild; the proper diagnosis and treatment of her bipolar disorder; her public lobbying for causes including mental health, AIDS awareness and nuclear disarmament; and a renewed television career that brought her three Emmys.

Her father, John Patrick Duke, was a handyman and cabby; her mother, the former Frances McMahon, was a cashier.

“Anna Marie is dead; you’re Patty now,” she was told, as she recalled in a memoir, “Call Me Anna”.As Patty Duke, she landed bit parts in films and on television before being cast in “The Miracle Worker.” To prepare her to audition for the part, the Rosses took to blindfolding her and moving the furniture around.

Playing the young Helen Keller – a rigorous role that required her to act, persuasively but without sentimentality, the part of a deaf-blind child subject to fearsome rages; to learn the manual alphabet; and to engage nightly in an ad-libbed, highly physical onstage fight with Ms. Bancroft that could last nearly 10 minutes – she won critical plaudits and enduring fame.

The show’s success – and Patty Lane’s popularity in particular – was something Ms. Duke came to deplore.

Ms. Duke said, fed her uppers and downers and introduced her to alcohol.

Ms. Duke’s survivors include her fourth husband, Mr. Pearce, an Army drill sergeant whom she married in 1986; her brother, Raymond; two sons, the actors Sean Astin and Mackenzie Astin; a stepdaughter, Charlene Gibson, from her marriage to Mr. Pearce; a son, Kevin, with Mr. Pearce; and six grandchildren.

Among Ms. Duke’s other television credits are the 1976 NBC mini-series “Captains and the Kings,” for which she won her second Emmy, and a 1979 TV adaptation of “The Miracle Worker” for which – playing Annie Sullivan to Melissa Gilbert’s Helen – she won her third.

Patty Duke