About the Doctors

Preeti Adeshara, M.D.

  • Dr. Adeshara completed her residency at University of Alabama at Birmingham, Selma Family Medicine Program.
  • She completed her Bachelor of Medicine and Bachelor of Surgery at the Medical College Baroda in India. She also has a Master’s degree in Reiki, a traditional Japanese method of healing.
  • Dr. Adeshara is board certified in Family Practice and sees patients of all ages.
  • Dr. Adeshara is an Assistant Professor at Western University of Health Sciences, Pomona, California in the Family Medicine Department.
  • She is a Certified Medical Examiner and is also certified in Advanced Obstetric and Pediatric Life Support. Dr. Adeshara is well vetted with academic and practical experience.
  • Dr. Adeshara is multi-lingual. She speaks English, Hindi, Gujarati, and Punjabi. She enjoys being outdoors, movies and eating out.

Naser W. Azar, M.D., IME, MRO, Certified Civil Surgeon, USCIS

  • Dr. Naser Azar has been providing exceptional medical care for over 25 years!
  • Received his medical degree from the prominent Odessa Medical Institute.
  • Received his medical degree from the prominent Odessa Medical Institute.
  • He completed international and domestic residency programs at the prestigious National Medical Institute, Ministry of Health, in Amman, Jordan as well as San Bernardino County Medical Center in San Bernardino, CA. Dr. Azar served as a Research Associate at the famous, Loma Linda University Medical Center.
  • Maintains a leadership role as the President and Medical Director for both Vista Medical Group offices in Chino and Corona.
  • Dr. Azar is a member of the American Medical Association (AMA) and the American College of Occupational and Environmental Medicine (ACOME).
  • Dr. Azar is a registered USCIS Civil Surgeon providing immigration examinations and an Independent Medical Examiner (IME) for multiple state and federal agencies.
  • He maintains a multitude of licenses and is a member of most HMOs and PPOs.
  • Dr. Azar passionately believes in accentuating the power of healing by combining the achievements of modern medicine and technology, with an unrivaled level of work ethic and uninterrupted perseverance to secure the most superior level of quality healthcare for each and every individual patient.
  • His medical skills extend beyond the standard of general and family practice and is able to provide his patients with a full range of comprehensive medicine including, but not limited to; the treatment of a wide range of injuries and illnesses, minor surgeries and lacerations, and complete physical assessment.
  • He accepts patients from the ages of two years and above.
  • Dr. Azar is fluent in Arabic, Russian and medical Spanish.

Talat Kahn, M.D.

  • Dr. Kahn received her Doctor of Medicine from Howard University College of Medicine in Washington, D.C.
  • She completed her residency at Lennox Hill Hospital in New York City.
  • Dr. Kahn is board certified in Internal Medicine and has over 20 years of clinical experience.
  • She is committed to providing compassionate, personalized medical care and well-being for all her patients.
  • Her languages are English, Spanish and Bengali.
  • Dr. Kahn’s special interests include travel and cultures.

Gilbert J. Martinez, M.D.

  • Since 1971, Dr. Gilbert Martinez has specialized in Family Practice, including pediatrics, adolescent medicine, geriatric medicine and occupational medicine.
  • As a Board Certified Family Practice physician, he provides a wealth of medical experience to Corona.
  • Dr. Martinez attended Northern College of Iowa for his undergraduate studies and earned his medical degree from the University of Iowa.
  • He completed an internship and Family Practice residency at San Bernardino County Hospital. He also earned a law degree from the University of La Verne School of Law.
  • Dr. Martinez has served as Chief of Staff of Doctors Hospital Montclair, president of the OSP Medical Group and president of the Chino Valley IPA, just to name a few.
  • He was appointed by the Governor of California to the California Board of Medical Assurance, now known as the Medical Board of California.
  • Dr. Martinez is also associated with a medical research company in Chino. He is a principal medical investigator, supervising medical research in patients with various medical conditions such as hypertension, diabetes mellitus, Alzheimer’s Disease, depression, schizophrenia, migraine headaches and back pain.

Masooma Mujeeb, M.D.

  • Dr. Mujeeb completed her residency in Family Medicine at Mercy Medical Center in Merced, California, an affiliate of the University of California at Davis.
  • Prior to residency, she completed medical school at FMH College of Medicine and Dentistry in Lahore, Pakistan where she graduated with honors and distinction in Pediatrics.
  • Incorporated with Family Medicine, Dr. Mujeeb utilizes her experience in women’s health and prenatal care.
  • Dr. Mujeeb is a member of the American Academy of Family Physicians, the California Academy of Family Physicians and the American Medical Association.
  • Dr. Mujeeb is fluent in English, Urdu and Punjabi.
  • Being very family focused, Dr. Mujeeb enjoys time with family. She and her husband enjoy outdoor activities and travels with their children.

Victoria Brown, PA-C

  • Victoria Brown completed her Master’s of Science degree in Physician Assistant Studies at Western University of Health Sciences, Pomona, California.
  • She has a Bachelor’s degree in Psychology from University of California, Los Angeles.
  • Victoria has clinical training in Orthopedics, Obstetrics and Gynecology, Urgent Care, Family Practice, Internal Medicine, Emergency Medicine, General Surgery and Pediatrics.
  • She is a member of the American Association of Physician Assistants.
  • In her free time, she enjoys traveling, cooking, and spending time with her family.

Maria Castillo, MPH, MSPA-C

  • Ms. Castillo attended the University of California Riverside for her undergraduate studies, earning a Bachelor of Science degree in Biochemistry with a minor in Political Science.
  • Maria went on to earn a Master’s of Public Health degree with emphasis in nutrition from Loma Linda University in Loma Linda and a Master’s of Science degree in Physician Assistant Studies at Western University of Health Sciences in Pomona.
  • She is a Board Certified physician assistant and is an active member of the California Association of Physician Assistants.
  • Ms. Castillo has years of experience in several aspects of family medical care, including OBGYN, chronic conditions, surgery, urgent care and emergency care.
  • She is an active mother of two girls who enjoys travel and crossfit training. Also an engaged member of her church and community.

Carrington Horton, PA-C, MPA

  • Carrington Horton is a graduate of Masters Studies from Loma Linda University, California licensed, and is a Nationally Board Certified Physician Assistant. In addition, Mr. Horton completed extensive course training with Physical Therapy and Psychology through Loma Linda University and Southwestern Adventist University, respectively.
  • PA Horton has over 12 years of direct patient care as a licensed clinician. His clinical work includes urgent care, pain management medicine, occupational medicine, entertainment medicine, and medical weight/lifestyle management.
  • Mr. Horton’s affection for active and healthy lifestyle fuels his continued training and active membership with the American Society of Bariatric Physicians.
  • Carrington Horton maintains a personal active lifestyle which includes love of sports, arts, music, travel, personal training, reading, and photography, just to name a few.
  • Mr. Horton also takes a deep personal interest in his community and philanthropy as it relates to the world as a whole. As a part of the Vista Team, PA Horton has been able to continue to give back to his community by offering the utmost service and care forged from years of medical experience.

Phuong Anh “Anne” La, PA-C

  • PA La graduated with a B.S. in Biological Sciences from the University of California, Irvine, and later pursued her rigorous physician assistant training by nationally known best-selling physician assistant book authors/professors at Hahnemann University (currently known as Drexel University).
  • Anne La is credentialed by many local IPAs and most insurance companies.
  • Anne La has been passionately caring for patients of all ages as a licensed physician assistant since 2000, with experience in a diverse number of specialties ranging from family practice, internal medicine, pediatrics, neurosciences to emergency medicine and occupational medicine, in all four counties in Southern California!
  • Ms. La joined Vista Medical Group in 2005 and proudly considered Vista her home! She is loved and respected by all of her patients.
  • She serves patients of all ages and provides family practice, urgent care and occupational care services. Ms. La believes in delivering the best quality healthcare for every single patient and loves to educate patients about their illnesses and health prevention. Her goal is to optimize the quality of life and health of all her patients.
  • Aside from her dedication to medicine, Ms. La loves to spend time with her family, volunteer in local schools, churches, boy scout and cub scout organizations, and the community where she lives.

Esther Loya, PA-C

  • Mrs. Loya graduated from Western University of Health Science in Pomona, California with a Master of Science in Physician Assistant Studies.
  • Mrs. Loya obtained her Bachelor of Science in Biology from the University of California, Riverside, California.
  • Mrs. Loya has a wide variety of clinical experience and training, including but not limited to, Urgent Care, Family Medicine, Internal Medicine, General Surgery, Gynecology and Pediatrics.
  • She is a member of the American Academy of Physician Assistants and the California Academy of Physician Assistants.
  • Along with her dedication to excellent patient care, Mrs. Loya enjoys a variety of community service activities and hobbies such as traveling, cooking and dancing.
  • Mrs. Loya is fluent in both English and Spanish and she practices in both our Corona and Chino clinics.

Michelle Matyseck, PA-C

  • Michelle Matyseck graduated from Western University of Health Sciences in Pomona, California with a Master’s degree in Physician Assistant Studies.
  • Ms. Matyseck obtained her Bachelor of Science degree in Biochemistry, with a minor in Chemistry from California State University, Long Beach.
  • Ms. Matyseck is a board certified Physician Assistant with a wide variety of clinical experience and training, including but not limited to Primary Care, Obstetrics and Gynecology, Pediatrics, Emergency Medicine, Internal Medicine and Dermatology. She is passionate about western medicine and natural methods of healing.
  • She is a member of California Academy of Physician Assistants.
  • Ms. Matyseck enjoys natural methods of improving health, hiking and walking her dogs, baking as a hobby and spending time with family.

Persephonie Tweten, PA-S

  • Persephonie Tweten graduated from Western University of Health Sciences in Pomona, California with a Master’s degree in Physician Assistant Studies.<.li>
  • Ms. Tweten obtained her Bachelor of Science degree in Biology from the University of La Verne in La Verne, California.
  • Ms. Tweten is a board certified Physician Assistant and a member of the California Academy of Physician Assistants.
  • Ms. Tweten has a wide variety of experience and training, including but not limited to, family medicine, urgent care, pediatrics, general surgery, emergency medicine, endocrinology, dermatology, obstetrics and gynecology, and internal medicine.
  • When Ms. Tweten isn’t busy at the clinic, she loves to go on adventures and enjoy life with her husband and two daughters.