Dr. Robert Hollenhorst of Rochester discovered a way to diagnose stroke and coronary diseases by looking into a patient's eye.

Hollenhorst did research on the crystals that lodge in the small arteries in the eye's retina. After he established what the crystals, or cholesterol plaques, were, they became useful in diagnosing other diseases.

Hollenhorst, for whom Hollenhorst plaques are named, died at his Rochester home on Jan. 10. The award-winning Mayo Clinic ophthalmologist was 94.

Hollenhorst's son, Dr. Robert Hollenhorst of Duluth, studied several months with his father at Mayo when he was serving his residency in ophthalmology.

"He was a great teacher, and his knowledge was limitless," said his son. "It was a joy to work with him."

The elder Hollenhorst wrote more than 90 scientific papers, made advances in neuro-ophthalmology, and led national medical associations.

He was awarded the Howe Medal for his work, a "rare" honor, said his son.

For 30 years, he was the consulting ophthalmologist to Minnesota State Services for the Blind, and he was an active leader in the state's Preschool Medical Survey of Vision and Hearing.

In 1941, the St. Cloud native graduated from the University of Minnesota School of Medicine.

During World War II, he served in the Army as a physician, making amphibious landings in New Guinea and the Philippines. He received the Bronze Star.

In the late 1940s, he did graduate medical studies at Mayo, and joined its staff in 1949.

In his early days, he performed many eye surgeries, but later turned to research and working with patients.

Dr. David Hanlon, retired Mayo hematologist, said Hollenhorst "loved" the clinic.

"He was quiet and unassuming but a very talented person," said Hanlon. "He made time for his friends, too."

His son, Thomas, of St. Louis Park, recalled the family singing and playing musical instruments together. And for many years, Hollenhorst was the soloist at Rochester's Church of St. John the Evangelist.

"Despite all the work, he was always there as a father," said his son.

He retired around 1980, living near Brainerd, where he enjoyed driving his boat and towing all the water skiers in his large family. In 1996, he moved back to Rochester.

His wife of 68 years, Alice, died in December. His son, the Rev. Mark Hollenhorst, died in 1993, and his son, Stephen Holllenhorst, died in 2000.

In addition to Tom and Robert, he is survived by sons Michael of Orono, John of Salt Lake City, and James of Saratoga, Calif.; daughters Mary Lazarus of Millbrae, Calif., and Kathleen Pohly of Pagosa Springs, Colo.; brother Dr. G. Donald Hollenhorst of Zion, Ill.; sisters Virginia Pleas of Seattle, Sister Bernice of Notre Dame, Ind., Edith Hering of Kailua Kona, Hawaii, and Elaine McKinley of Bay Village, Ohio; 21 grandchildren, and 13 great-grandchildren.

Services will be held at 11 a.m. on June 18 at the Fort Snelling Historic Chapel.