A prominent New York doctor swindled a 102-year-old Park Avenue patient, writing himself into her will and installing health care aides who mistreat the widow, a new lawsuit charges.

Donna Spears, a longtime friend of centenarian Helen Schlesinger, claims in her Manhattan civil suit that New York-Presbyterian physician Dr. Lawson Moyer has broken the law by both treating the 470 Park Ave. resident and appointing himself as her power of attorney.

“Moyer is making decisions for Helen that are not in her best interests,” Spears says in the suit.

Spears, of Wall Township, NJ, says she has known Schlesinger for 65 years. The frail woman, whose husband died in the 1950s, cannot get around on her own and requires 24-hour care.

In a 2003 will, Spears and a family member were designated to inherit the woman’s entire multimillion-dollar estate — save for a $10,000 bequest to the Salvation Army.

But shortly after Moyer became Schlesinger’s primary care doctor in 2010, the suit says, Schlesinger signed a new document “against [her] wishes” that left him $100,000, slashed Spears’ share to $25,000 and gave the rest to various charities.

Spears says Moyer hired nurses who have neglected and mentally abused the childless widow.

Spears wants a judge to appoint a guardian for Schlesinger.

Moyer did not return calls for comment.