Ruby Kathryn Daniel, eye surgeon, was born in Duncanville, Texas, around 1902, the daughter of Robert Harry and Beulah May (Fite) Daniel. After attending Southern Methodist University and the University of Texas, she enrolled in Baylor University College of Medicine in Dallas (now Baylor College of Medicine, Houston), where she graduated in 1928. She interned at Lane-Stanford Teaching Hospital in San Francisco and the University of Chicago and did her residency in Chicago. Before returning to Texas in 1939 she established herself as an eye surgeon; she was a fellow in ophthalmology at the Mayo Clinic in Rochester, Minnesota, from 1934 to 1936 and taught on the staff of the Union Medical College in Peking, China, in 1936–37. The following year she taught in Vellore, India, before returning to the Mayo Clinic in 1938 as a first assistant in ophthalmology. Also in 1938 she earned a master's degree from the University of Minnesota.
In 1939 she moved to Dallas and opened a private practice in ophthalmology. In conjunction with her practice, she served as chief medical consultant for the Lighthouse for the Blind and chief ophthalmologist for the Pilot School for the Deaf. She was a member of the staff at five Dallas-area hospitals and in 1943 joined the teaching staff of the Southwestern Medical Foundation in Dallas (now the University of Texas Southwestern Medical School) as assistant clinical professor of ophthalmology. During her career she founded two philanthropic organizations for rehabilitating and salvaging eyes and wrote several scholarly articles on the eye. She also delivered numerous papers on the science of the eye throughout the United States, Europe, and South and Central America.
Dr. Daniel was a diplomate of the American Board of Ophthalmology and a fellow of the American College of Surgeons. She belonged to the International College of Surgeons, the American Medical Association, and the American Association for the Advancement of Science. She was a president of the Dallas Academy of Ophthalmology and Otolaryngology and a member of the Dallas County Medical Society. She was a Methodist and was active in numerous civic and social clubs in Dallas. She died in Dallas on February 13, 1978, and was buried at Restland Memorial Park in Dallas.