Cmdr. Donal M. Billig, the former chief heart surgeon at Bethesda Naval Hospital, took the witness stand yesterday for the fourth time to defend himself on five counts of involuntary manslaughter and dispute claims that an injury to his right eye impaired his ability to operate.

Billig is expected to take the stand again today as prosecutors cross-examine his statements made last week in the general court-martial, which began in early January.

His testimony yesterday followed statements by expert witness, Dr. Paul J. Corso Jr., a cardiothoracic surgeon associated with Washington Hospital Center.

Corso, who reviewed records of the Bethesda operations, said that Billig used techniques that were acceptable standards of practice but agreed that "there were some technical difficulties" with the five patient deaths that prompted the charges against him.

Corso would not make generalizations for the prosecution or the defense, and shied away from judging Billig's work.

"You can take five cases out of any competent surgeon around and you'll be able to find problems," Corso said.

Billig, who performed 256 major heart operations during 1983 and 1984 at Bethesda, said he conducted those operations five years after he was struck in the right eye with a tennis ball, an injury that caused bleeding and scarred his retina.

In the months after the injury, Billig said, he practiced for hours to adjust to his vision problem and abstained from surgery until he felt confident with his skill.

After the accident, which occurred in November 1978 while Billig was practicing in New Jersey, the surgeon underwent a 10-day stay at a New York hospital where he was found to have a retinal hemorrhage and visual field defects. His sight in that eye was recently diagnosed as correctable to 20/400.

"I spent about seven hours a week practicing" eye exercises and hand-eye coordination skills, in order to again feel comfortable about operating within months after the accident, Billig said yesterday.

"I know one thing," Billig said. "I don't have normal vision in my right eye. And I've worked very hard to compensate for that . . . my patient statistics bear that out."