He is asking for $10 million in damages.
Natale's past - an admitted role in at least eight murders - didn't mean he wasn't entitled to the same medical care as any inmate, his lawyer said.
"The man is who is he is. I can't just turn him into a bed of roses," the lawyer, J. Conor Corcoran, said Wednesday. "But he's entitled to his dignity. And that's precisely what they took from him."
The suit marks the latest public glimpse of the ex-boss who ended a 13-year prison term in 2011 and at last word was shopping his memoir. The book's plot is unlikely to surprise anyone who's followed the slow demise of the mob: South Jersey-based wiseguy uses violence to climb the ranks, becomes the leader, then cuts a deal to spare himself life in prison.
Natale testified as a government witness in four trials between 2000 and 2004, including two for his onetime ally and successor as leader of the local crime family, Joseph "Skinny Joey" Merlino.
It was during those years of cooperation, Natale asserts, that his eyesight began to fail but that his pleas for help were ignored.
Natale claims that his daughter-in-law, a nurse, won permission for him to be examined by a specialist at the Wills Eye Institute in Center City during a stretch when Natale was testifying just a few blocks away, at the U.S. District Courthouse in Philadelphia.
According to the lawsuit, Assistant U.S. Attorney Mary Futcher, one of the prosecutors, "intentionally interfered and/or refused to allow" the visit and directed U.S. marshals and prison officials not to take Natale to the exam.
The suit also claims prison officials at the Allenwood, Pa., federal prison "continually failed" to provide a proper diagnosis or treatment for Natale's failing eyesight or allow him to see a specialist, even after he learned in 2007 that prison files described him as legally blind.
He was released in 2011.
A spokeswoman for U.S. Attorney Zane David Memeger said government lawyers would not comment on the suit, except to note that they have 60 days to file a response to the claims.
Edwin J. Jacobs Jr., a lawyer for Merlino who cross-examined Natale during two trials, said he didn't recall Natale's fading eyesight coming up in either case.
Jacobs has his own opinion of Natale's credibility - "I got two juries of impartial citizens to disbelieve him," he said - but said he couldn't be considered an advocate for his causes or in a position to judge the turncoat's health.
Corcoran said he filed the suit after the Justice Department failed to respond to an administrative complaint he filed on Natale's behalf last year.
The case is not unlike hundreds, if not thousands, of prisoner civil rights complaints filed each year in the local court system. But, Corcoran acknowledged, "what makes it unusual is who the plaintiff is."
He said he couldn't make that plaintiff available for an interview and he declined to say where Natale now lives except that he is "somewhere between Maine and Florida." His client has never been in the witness protection program, he said.
The lawyer did say Natale lives with relatives - that would include his 80-year-old wife, according to an interview the couple gave last summer to Philadelphia Weekly. But with limited peripheral vision, there's little Natale can do these days, his lawyer said.
Corcoran insisted the blindness was preventable. He said early treatment helped his own mother retain her eyesight, and could have done the same for Natale.
"They really, really interfered with the possibility of saving this man's eyesight," he said, "and I'm going to rake them over the coals for it."
Contact John P. Martin at 215-925-2649, at firstname.lastname@example.org, or @JPMartinInky on Twitter.