Dr. Tuai attended Ohio State University, College of Medicine after he received his Undergraduate Degree in Biochemistry at UC Davis in 1992. He completed his general surgery residency at UC San Francisco/Fresno, where he spent a year as a clinical instructor in the Department of Surgery, before beginning a private practice in Chino. He joined the Group in December, 2004.Dr. Tuai is a Board Certified surgeon and a Fellow of the American College of Surgeons who has extensive experience with advanced laparoscopic and minimally invasive techniques including robotic surgery.Dr. Tuai's passion is minimally invasive surgeries, especially involving the colon, stomach, gall bladder, and hernias. He is fluent in Mandarin Chinese and Korean.Offers high-quality, individualized care with compassion. Believes communication and collaboration with patients is the foundation for effective relationships. Through effective education, patients are empowered to partner in their care and achieve their health goals. Dr. Tuai is rated as an Advanced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Hernia, Gallstones, Choledocholithiasis, Hernia Surgery, and Ileostomy.

Dr. Eisner attended medical school at New York University after receiving his undergraduate degree in Integrative Biology at U.C. Berkeley. He completed his General Surgery residency at U.C. San Diego. Dr. Eisner is a board eligible general surgeon with extensive experience in general surgical procedures including gastrointestinal (esophageal, stomach, small intestine, colon, rectal and anus), esophageal reflux, hernia (inguinal, umbilical, and ventral), skin and soft tissue (skin cancer and melanoma, lipoma, pilonidal), breast (benign and cancer) with advanced laparoscopic, minimally invasive, endoscopic, and robotic surgery skills.  As the newest member of our surgical team and a Southern California native, Dr. Eisner spends his off time surfing, rock climbing, and hiking. He is conversant in Spanish and fluent in French. Dr. Eisner is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Gallstones, Hernia, Gallbladder Disease, Bladder Reconstruction, and Gallbladder Removal.

Laya Nasrollah is a Gastroenterologist in Ventura, California. Dr. Nasrollah is rated as an Advanced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. Her top areas of expertise are Gastroesophageal Reflux Disease (GERD), Familial Adenomatous Polyposis, Diarrhea, Endoscopy, and Gastrectomy. Dr. Nasrollah is currently accepting new patients.

Samantha Wu is a General Surgeon in Oxnard, California. Dr. Wu has been practicing medicine for over 10 years and is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. Her top areas of expertise are Gallstones, Choledocholithiasis, Gallbladder Disease, and Retroperitoneal Inflammation. Dr. Wu is currently accepting new patients.

Donald Miller is a Gastroenterologist in Oxnard, California. Dr. Miller is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Gas Bloat Syndrome, Non-Alcoholic Fatty Liver Disease, Visceromegaly, Endoscopy, and Gastrectomy.

Justin Marasigan is a Gastroenterologist in Oxnard, California. Dr. Marasigan is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Familial Adenomatous Polyposis, Turcot Syndrome, Gardner Syndrome, Gastrectomy, and Colonoscopy. Dr. Marasigan is currently accepting new patients.

John Billesdon is a Gastroenterologist in Oxnard, California. Dr. Billesdon is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Gastrointestinal Bleeding, Colitis, Viral Gastroenteritis, Endoscopy, and Gastrectomy.

Patrick Mccarty is a General Surgeon in Ventura, California. Dr. Mccarty is rated as an Advanced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Hernia, Gallstones, Choledocholithiasis, Gallbladder Removal, and Endoscopy. Dr. Mccarty is currently accepting new patients.

Offers high-quality, individualized care with compassion. Believes communication and collaboration with patients is the foundation for effective relationships. Through effective education, patients are empowered to partner in their care and achieve their health goals. Dr. Dixon is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Choledocholithiasis, Hernia, Breast Cancer, Hernia Surgery, and Colostomy.

Offers high-quality, individualized care with compassion. Believes communication and collaboration with patients is the foundation for effective relationships. Through effective education, patients are empowered to partner in their care and achieve their health goals. Dr. Lopresti is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Choledocholithiasis, Gallstones, Gallbladder Disease, Bladder Reconstruction, and Hernia Surgery.

Kip Lyche is a Gastroenterologist in Ventura, California. Dr. Lyche is rated as an Advanced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Esophageal Varices, Enlarged Liver, Visceromegaly, Endoscopy, and Colonoscopy. Dr. Lyche is currently accepting new patients.

Benito Pedraza is a Gastroenterologist in Ventura, California. Dr. Pedraza is rated as an Advanced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Familial Adenomatous Polyposis, Gastrointestinal Bleeding, Gastric Dysmotility, Endoscopy, and Gastrectomy. Dr. Pedraza is currently accepting new patients.

Charles Menz is a Gastroenterologist in Ventura, California. Dr. Menz is rated as an Advanced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Familial Adenomatous Polyposis, Hepatitis C, Gastroesophageal Reflux Disease (GERD), Endoscopy, and Gastrostomy. Dr. Menz is currently accepting new patients.

Dr. Billy is the leading Lap-Band, laparoscopic gastric bypass and laparoscopic gastric sleeve surgeon in Ventura and Santa Barbara County. Dr. Billy relocated his practice to Ventura in July of 2002. Prior to that he had established himself as one of the premier laparoscopic surgeons in the Sacramento and Sierra Nevada region of Northern California. Dr. Billy was instrumental in developing the bariatric surgery centers at Sutter General Hospital and Sutter Roseville Medical Centers. He is currently director of Bariatric Surgery at St. John's Regional Medical Center, a recognized bariatric Center of Excellence by the Surgery Review Committee, Medicare, Blue Cross, Blue Shield and Health Net. St. Johns Regional Medical Center is located in Oxnard California. Dr. Billy also serves as the Medical Director of the Community Memorial Hospital, a Surgical Review Corporation accredited Bariatric Center of Excellence, located in Ventura, California. Dr. Billy obtained his undergraduate degree in Molecular Biology at the University of California, Berkeley. He subsequently received his medical degree at the University of California, Davis School of Medicine. Dr. Billy received additional training in the techniques of the Lap-Band system prior to its release by the FDA in 2001. He is actively involved as a teaching faculty member for placement of the Lap-Band® system and has educated and proctored dozens of surgeons throughout the west as part of their educational training. Dr. Billy has been a faculty member at numerous national educational events and surgeon training workshops. He has been a featured speaker at the annual meeting of the American Society of Metabolic and Bariatric Surgery and was a contributing author on the recently released SAGES Bariatric Surgery Manual published by the Society of American Gastrointestinal and Endoscopic Surgeons. Dr. Billy has an international reputation and has lectured and taught principles of bariatric surgery in Mexico, Taiwan and India.Offers high-quality, individualized care with compassion. Believes communication and collaboration with patients is the foundation for effective relationships. Through effective education, patients are empowered to partner in their care and achieve their health goals.In May 2022 Dr. Billy was elected to the American Society for Metabolic and Bariatric Surgery Council, the largest and most prestigious National Society for metabolic and bariatric surgery.The executive council consists of 8 ASMBS members who represent the leadership of the National Society.The vision of the society is to improve public health and well being by lessening the burden of the disease of obesity and related diseases throughout the world. Dr. Billy is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Obesity, Malabsorption, Hiatal Hernia, Gastrectomy, and Sleeve Gastrectomy.

Dr. Micha Rojany was born and raised in Southern California. He received his undergraduate degree from the University of California, Berkeley. He attended USC Medical School and completed his internship and residency at Cedars-Sinai Medical Center in Los Angeles. His fellowship in Gastroenterology was completed at the University of California, Davis.Dr. Rojany has practiced in Ventura County since 2006 and is an active member of the local medical community and hospital staff at St. John's Regional Medical Center in Oxnard, and Pleasant Valley Hospital, in Camarillo. He enjoys practicing as a Gastroenterologist with special interests in inflammatory bowel disease and biliary tract diseases.As a Gastroenterologist, Dr. Rojany enjoys the depth and breadth of his field. He takes pride in providing excellent care while taking care of his patients and meeting their needs as a community specialist in digestive diseases. Dr. Rojany is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Familial Adenomatous Polyposis, Gastrointestinal Bleeding, Angiodysplasia of the Colon, Endoscopy, and Gastrectomy.

Dr. Karen Simon received her B.A. from Stanford University in 1996. She then attended Northwestern University for medical school. She completed her residency at Cedars-Sinai Medical Center in 2004 and her fellowship at UCLA and Cedars in 2008.Dr. Simon has proudly been serving patients in Ventura County since 2008 and is very involved in field research. Dr. Simon is also a speaker for Exact Sciences on behalf of Cologuard and is actively associated in research studies. She is a part of the Takeda Chloride Channel Council and a speaker for Amitiza, as well.She enjoys educating the doctors and the community as a lecturer on topics such as colorectal cancer screening at St. John's Hospital, where she is also a part of the Ethics Committee.Dr. Simon aims specifically to work with patients to discover the problem and develop a treatment strategy. She has a particular interest in Celiac Disease, Inflammatory Bowel Disease (IBD), and a passion for improving colorectal cancer detection.She is dedicated to developing a relationship with patients by utilizing education and mutual information sharing. Dr. Simon is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. Her top areas of expertise are Gastroesophageal Reflux Disease (GERD), Familial Adenomatous Polyposis, Painful Swallowing, Endoscopy, and Colonoscopy.

I am committed to providing the highest level of quality and compassion in surgical care to the residents of Ventura County. I offer the most evidence-based and modern surgical techniques available in order to provide superior care and achieve better outcomes for my patients. Furthermore, I am dedicated to providing a patient-centered care experience that enables each patient to make a well-informed decision about their care. Dr. Brand is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. Her top areas of expertise are Hernia, Peptic Ulcer, Necrosis, Gallbladder Removal, and Hernia Surgery.

Joel Alpern is a Gastroenterologist in Ventura, California. Dr. Alpern is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Gastric Dysmotility, Gastroesophageal Reflux Disease (GERD), Diarrhea, Endoscopy, and Gastrectomy. Dr. Alpern is currently accepting new patients.

Chetan Gondha is a Gastroenterologist in Ventura, California. Dr. Gondha is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Familial Adenomatous Polyposis, Diarrhea, Trichohepatoenteric Syndrome, Endoscopy, and Colonoscopy.

Stephen Covington is a Gastroenterologist in Ventura, California. Dr. Covington is rated as an Experienced provider by MediFind in the treatment of Congenital Diaphragmatic Hernia. His top areas of expertise are Hepatitis, Hepatitis C, Gastroesophageal Reflux Disease (GERD), Endoscopy, and Gastrectomy. Dr. Covington is currently accepting new patients.