Current Residents


Daniel Agraz, MD
Daniel Agraz, MD

Nebraska is home for Daniel Agraz. He attended the University of Nebraska-Lincoln, where he
graduated with Highest Distinction and Honors with degrees in Biochemistry and Spanish. He
obtained his medical degree from the University of Nebraska Medical Center’s College of Medicine and completed his transitional year in Family Medicine at Broadlawns Medical Center in Des Moines, IA.

Daniel's interests include SCCA Solo racing, fantasy football, running and cycling. During the fall, you can find him attending Nebraska volleyball and football games. Why Nebraska?  In the great words of Husker Athletics: There is no place like NEBRASKA.



Brent Deibert, MD
Brent Deibert, MD

Brent grew up in Colby, Kansas and throughout the Midwest as part of his father’s custom harvesting crew. He attended Kansas Wesleyan University, where he double majored in Chemistry and Biology. After graduating college, Brent worked as a wildlife biologist across the country for the NPS, DOD, and USDA. He obtained his medical degree from the University of Kansas. He completed his internship at UNMC in Internal Medicine, where he met his wife.

In his free time, he enjoys exercise, spending time outside, finding new restaurants in Omaha, KU basketball, and traveling around the country to visit national parks.


Colby Argo, MD
Colby Argo, MD

Colby is a native Nebraskan, having grown up outside of the sprawling metropolis of Liberty, population 76. After graduating from the University of Nebraska-Lincoln with degrees in Biology and Political Science, he earned his medical degree from the University of Nebraska Medical Center. Colby completed his transitional year in Sioux Falls, South Dakota, before joining UNMC. 

Outside of work, Colby and his wife spend their time fussing about their house and discovering new places to eat. In his free time, you can find him on the golf course or running trail, listening to podcasts, or attempting to be well-read.



Santi Karnam, MD

Santi was born in Pennsylvania but raised in India until the age of eight, when he moved back with his family to the U.S.  After graduating from Temple University with a degree in Cellular and Molecular Neuroscience, he then went on to earn his medical degree from Creighton University School of Medicine. He completed his intern year at St. Joseph's Hospital and Medical Center in Phoenix, Arizona before joining UNMC.

In his spare time, he enjoys video games, basketball, frisbee golf, cooking, and ethnic cuisine.


William Wagner, MD 

Will grew up in Superior, Colorado. He received his undergraduate degree from Brigham Young University, where he studied Exercise Science. After graduating, he attended Virginia Commonwealth School of Medicine and was selected to the Alpha Omega Alpha Honor Society. He completed his intern year at UNMC.

Outside of work, Will enjoys spending time with his wife and young son. He also enjoys snowboarding, running, and of course Husker football. Go Big Red!


 de stefano
Vinicius S. De Stefano, MD, PhD

Vinny was born and raised in Sao Paulo, Brazil. He received his MD from the Federal University of Sao Paulo, where he also completed his first Ophthalmology residency and a refractive surgery fellowship. In 2015, he moved to the U.S. and completed a postdoctoral fellowship in corneal biomechanics at the Cleveland Clinic. He defended his Ph.D. thesis in 2018 and finished a year-long cornea fellowship at the Medical University of South Carolina in June 2019. Vinny then decided that he preferred to live and practice in the U.S., so he is now completing his second residency in Ophthalmology at UNMC.

In his free time, Vinny enjoys spending time with his family, going to sporting events, and snowboarding.



Christine Ryu, MD 

Christine Ryu lived in multiple states growing up, including Nebraska. She attended Dartmouth College and graduated with a degree in anthropology with honors. Afterwards, she worked as an English teacher in France. She earned her medical degree at Keck School of Medicine at the University of Southern California and was selected to Alpha Omega Alpha Honor Society. Christine is currently completing her internship at UNMC.

In her free time, Christine enjoys hiking, cooking, baking, especially cooking and baking with citrus.



Rena Xu, MD, PhD
Rena Xu, MD, PhD

Rena Xu was born and raised on a little farm near Nanjing, China. She received her MD from Nanjing Medical University, after which she moved to America to pursue her PhD in Vision Science at Indiana University. She then received an NIH K08 award and spent two years completing postdoctoral research in myopia before beginning her internship at UNMC.

Rena loves spending time with her husband, Amos, and their two children, Camy and Andrew. She enjoys bike riding with family and exploring different recipes, especially Indian, Thai, and of course Chinese food.