About Us

GreatDef was honed over a decade holding the digital image “bull by the tail” but ultimately enabling us to provide the simple GreatDef clinical image capturing solution at a most reasonable price.  

GreatDef spans all ranges of high definition imaging and can be presented to portable devices for immediate presentation.

Our CEO - Dr. Michael J. O'Leary

Our CTO - Marc Perez

Our GC   - Zion Maffeo

Dr. Michael J. O'Leary

Marc Perez

 At the Senta Clinic, Dr. Michael O’Leary specializes in diseases of the ear and balance. He helped create the new Center for Hearing – ChEARS! offering hearing healthcare with advanced hearing aids, assistive listening devices and implants. His skull base role is that of neurotologist, focusing on tumors of the lateral skull base such as acoustic neuromas and meningiomas. He is also a nationally-recognized leader in the development of minimally invasive techniques including the endoscopic removal of pituitary tumors.

Michael J. O’Leary, MD was born in 1954, in Denver, Colorado and grew up in New York. He began his medical career there, earning his bachelor’s degree in biology from the University of Rochester in 1972 (cum laude) followed by his doctorate of medicine from Georgetown Univ., Washington, DC in 1980 (magna cum laude).

During medical school in 1976 he entered the US Navy as an Ensign (0-1), the start of a 24-year career. Following internship and residency at the Naval Hospital San Diego in 1986, he was assigned as Chief, Otolaryngology/Head and Neck Surgery at Naval Hospital Newport, RI until 1989 (the “head and tail” of the department). He then underwent subspecialty training in Neurotology/Skull Base Surgery beginning as a Clinical Fellow at the prestigious House Ear Clinic in Los Angeles. This was followed by a year of Microvascular surgery at Washington University in St. Louis, MO with Dr. Richard E. Hayden. In 1991 he returned to Naval Hospital San Diego as the Chief, Neurotology/Skull Base Surgery. Upon his retirement in 2000 as a Captain (0-6), his neurotology division had grown from one to a team of over 25 individuals, performing pioneering clinical and basic science research focused on disorders of the ear and skull base.

Doctor O’Leary is board-certified by the American Board of Otolaryngology/Head & Neck Surgery, a fellow of the American College of Surgeons, and a clinical assistant professor of surgery with the Uniformed Services University of Health Science. He is a past chairman of the Skull Base Surgery committee of the American Academy of Otolaryngology/Head & Neck surgery and has served as consultant to the Surgeons General.

Honors include membership in AOA – the honor medical society, and he is a recent recipient of the AAO/HNS honor award. He is a member of numerous medical associations, and has served as president of the San Diego Society of Otolaryngology/Head & Neck Surgery, the Society of Military Otolaryngologists, and the House Fellowship Alumni group. Military decorations include the Navy Commendation Medal, the Navy Achievement Medal and the Navy Meritorious Service Medal. He is also an Eagle Scout.

Doctor O’Leary has authored or presented more than 90 scientific works focused on the ear and skull base, including 10 book chapters. He is a champion of digital advances in medicine and an opinion leader regarding process improvement and practice effectiveness in medicine.



Hearing & Balance Disorders

Skull Base Surgery

Surfer’s Ear

Cochlear & BAHA Implants

Meniere’s Disease

Pituitary Tumors



 Meritorious Service Medal, 2000

 Navy Commendation Medal, 1987

 Navy Achievement Medal, 1982

 Meritorious Service Award 1992

 Expert Pistol 1994, Expert Rifleman 1992

 Battle Excellence Award 1981, 1982

 AOA (Honor Medical Society), 1980

 Eagle Scout, 1969


 Castle Connolly Southern California Top Doctors 2012

 U.S.News & World Report Top Doctors 2012

 Honor Award, American Academy Otolaryngology/Head & Neck Surgery, 2000

 Staff of the Year Award, NMCSD ENT Residents; 1999

 1st Prize, San Diego AOHNS Resident Paper Competitions-1984,1986

 1st Prize, Military AOHNS Resident Paper Competitions-1984,1986


“Healthcare Quality Dashboard”


CMS Quality Standards Ad Hoc Committee (2003 to present)

 Skull Base Surgery Committee, Am. Academy of Otolaryngology

 Chairman (10/96-99), member (9/92-9/96)

 Informatics Committee, Am. Academy of Otolaryngology (11/92-9/98)

 Provider Profiling Working Group, NMC San Diego (9/96-98)

 Teleconsultation Working Group, Chairman, NMC San Diego(6/96-4/97

 Customer Service Committee, Co-Chairman, NMC San Diego:6/94-5/95

 Continuing Medical Education Committee, NMC San Diego (9/91-3/97)

 Medical Records/Utilization Review Committee, Chairman,

 Naval Hospital, Newport, RI (6/87-8/88)


CCHAT School for the Hearing-Impaired, Encinitas, CA (6/00-02)

 American Red Cross Fibrin Sealant Medical Advisory Board (3/00-02)


Golf, Bicycling, Windsurfing, and History

An IT Professional for 20+ years, Marc grew up in Southern California and has lived in Northern San Diego County most of his life. In high school, he earned a full Naval ROTC Scholarship. After graduating San Marcos High School, he started his college career and earned a bachelor's degree in computer science from Boston University. Upon college graduation, he was commissioned an Officer in the United Stated Navy. He reported to Pensacola Florida for flight training. He earned his Naval Flight Officer Wings and was designed an A-6 Intruder Bombardier/Navigator. After serving time in the military stationed at Virginia Beach, Virginia, Marc left the military and started his IT career.

He has spent most of his career working system engineering positions both in the commercial and military contract worlds. Marc has been fortunate to work on and complete many projects that have helped the healthcare industry and our troops abroad.

Marc has many IT accolades including special recognition from the Assistant Secretary of Defense for outstanding work supporting operation desert storm.

He currently holds Security+, Apple, and numerous Microsoft Certifications.

Marc currently holds an active secret clearance.

Most recently, he was accepted to the graduate program at San Diego State University andfinished his Masters of Science Degree in Information Sciences (MSIS) at the School of Business.

Zion Maffeo

Zion Maffeo is a patent attorney with experience advising companies on protecting, commercializing, and licensing corporate IP assets.  In his previous role, Zion served as the sole patent attorney for Esri, a world leader in GIS software.  At Esri, Zion oversaw the growth of Esri’s global patent portfolio and served as the lead attorney supporting Esri’s Startup and Venture Capital.  Additionally, he provided IP litigation support IP related matters.  

Before he joined the legal profession, Zion worked for more than ten years on software optimization and network security projects for employers ranging in size from 5 person startups to global multinational enterprises.  He served four years as a cryptologist in the U.S. Navy and also worked for a variety of government, academic, and commercial organizations.  In his current role as a patent attorney, Zion leverages these technical skills to efficiently analyze and manage invention disclosures covering complex and strategically essential methods while providing counsel on IP issues.  

Zion earned a J.D. from the University of California Hastings College of the Law and a B.S. in Chemistry Computation from the University of Texas at Austin.  He is licensed to practice law both in California and before the United States Patent Office.  In his spare time he rebuilds and restores classic cars.