Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum Sole proprietor

Dr. John Ilsun Ryu, O.D.

Optometrist in Simi Valley, CA · enumerated 2006 · practices at Summit Optometric Eyecare.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1609946847

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Registry record

Entity type Individual (Type 1)

Name Dr. John Ilsun Ryu

Credential O.D.

Sex Male

Practice address Simi Valley, CA, 93065

Phone (626) 376-3513

Fax (905) 250-1001

Enumeration date Nov 8, 2006

Last updated in NPPES Jul 15, 2024

Street address withheld — NPPES sole-proprietor addresses can be home addresses. See our data policy.

Taxonomy & licenses

152W00000X Optometrist Eye and Vision Services Providers · License 11209T (CA) Primary

OD — Doctor of Optometry: A licensed optometrist providing primary vision care, eye exams, and corrective lenses. About the OD credential

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes — even if the provider moves or changes specialty.

Read the full guide → Validate an NPI →

Frequently asked questions

Is NPI 1609946847 active?

Yes — as of the latest NPPES snapshot, NPI 1609946847 is active (record last updated 2024-07-15).

How do I verify John Ryu's NPI record?

Cross-check NPI 1609946847 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

Other providers at this practice address

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Summit Optometric Eyecare Optometrist · Simi Valley, CA NPI 1053757039

Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2024-07-15.