Quick answers
- Where does Mark T. Williams see patients?
- Medicare's clinician data lists 3 practice locations, including Orange, CA, Yorba Linda, CA and Anaheim, CA. Call before your visit to confirm the address.
- What is Mark T. Williams's specialty?
- Medicare lists Ophthalmology as the primary specialty.
- Does Mark T. Williams accept Medicare assignment?
- Yes. Medicare's clinician data says Mark T. Williams accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of 2026-10-02. Ask the office to confirm before your visit.
- What is the phone number for Mark T. Williams?
- (714) 738-4621, as listed in official Medicare / NPI Registry data.
- What is Mark T. Williams's NPI number?
- 1780118802. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Practice locations
Addresses where Mark T. Williams is enrolled with Medicare (CMS data updated 2026-10-02).
- 1310 W Stewart Dr, Suite 303Orange, CA 92868 (714) 738‑4621
- 22550 Savi Ranch PkwyYorba Linda, CA 92887 (714) 685‑3500
- 5475 E La Palma AveAnaheim, CA 92807 (714) 279‑6088
Group practices
Medicare enrollment lists Mark T. Williams as a member of this group (CMS data updated 2026-10-02).
- Southern California Permanente Medical Group11,293 clinicians in the group
Specialties
- Ophthalmologyprimary
Other ophthalmologists in Orange
Clinicians with the same Medicare primary specialty in Orange, CA — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | University Of California, San Francisco School Of Medicine |
| Graduation year | 2017 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1780118802 |
| Corrections | Report an error or suggest an update → |
Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.
Sources
- National Downloadable File (Doctors and Clinicians) — CMS, data updated 2026-10-02, retrieved 2026-10-29
- NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
- Medicare Care Compare — official Medicare tool to look up clinicians