Dr. Dorothy Behner Holmes, 78, a retired ophthalmologist who had an earlier career as a bacteriologist and biology instructor and who served as a physician treating injured civilians in Vietnam during the war there, died of cancer Thursday at Washington Hospital Center.

Before becoming an ophthalmologist, Dr. Holmes worked as an assistant in bacteriology for New York city, as an instructor in biology and bacteriology for the New York State Commission for the Blind and as an orthoptist (eye specialist) for the New York State Health Department.

After she and her husband, Dr. Oliver W. Holmes, moved to Washington about 1933, she commuted between her home here, her career in New York an her medical studies in Pennsylvania and Baltimore.

Dr. Holmes maintained a private opthalmology practice here from 1944 until her retirement in 1973. She was a member of the staff of the Episcopal Eye, Ear and Throat Hospital, which later became part of Washington Hospital Center.

Born in Newton, Iowa, she grew up in Glasgow, Montana, and graduated from the University of Montana in 1925. She later earned master's and doctoral degrees from New York University.

In 1937, she turned in medicine and earned a medical degree from the University of Pennsylvania in 1941. She was an intern and resident at the Johns Hopkins Unversity Wilmer Ophthalmological Institute from 1941 to 1944.

In 1969, under the auspices of the American Medical Association and the State Department, Dr. Holmes went to Vietnam, where she and other physicans treated injured civilians.

Dr. Holmes, who contributed articles to medical journals, was a member of the American Medical Association, the Women's Medical Society, the Association for Research in Ophthalmology and the Pan American Association of Ophthalmology.

Besides her husband of 53 years, of Washington, survivors include a son, Benson Venables of Omaha; a daughter, Helen Victoria Morrison of Honolulu; her mother, Maude Clark Venables Behner, and two sisters, Ruth Allman and Carol Morrison, all of Billings, Mont., an another sister, Alice Way of Pasadena, Calif.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.