WASHINGTON (AP) _ Prosecutors told a nine-officer jury that five of Navy surgeon Donal Billig's heart surgery patients died not from risky operations but because of the doctor's poor eyesight, bad judgment and faulty technique.

''Although there is always some risk in surgery, they were not killed by risk, they were killed by mistakes of the accused,'' chief prosecutor, Marine Col. Edward L. Miller told the jury in his opening statement to the court- martial of Billig.

Billig's defense attorney, meanwhile, called the surgeon as ''an innocent member of his profession.''

The jury, having heard opening arguments, was off until Monday when the first evidence will be presented.

Billig is charged with involuntary manslaughter in the cases of the five patients who died either on the operating table or soon after coming out of surgery.

Billig, 54, former chief of cardiothoracic surgery at Bethesda Naval Hospital - where President Reagan had his cancer operation - also is charged with 24 counts of dereliction of duty. The trial may run into March, the jury was told.

The members of the panel are a rear admiral and eight Navy captains, one a woman nurse. Three of the other captains are doctors.

Defense lawyer Denver Graham told the jury that one of the first witnesses will bring ''pickled human hearts'' for them to examine. The hearts are not those of Billig's patients.

Graham described Billig as ''an innocent member of his profession, board- certified in two specialties, as an officer of the United States Navy and certainly as a gentleman. He acted in accord with the highest tradition of medicine.''

But Miller said the case was ''about lack of competency, a case about errors in surgical technique, a case about negligence in surgery, a case about the lack of physical ability to do the surgery,'' Miller said, adding:

''The accused wrongfully killed because of bad eyesight, bad judgment, poor surgical technique and the inability to recognize his limitations.''