Crystal Sin Yi Cheung
Crystal Sin Yi Cheung is a Pediatric Ophthalmology and Strabismus Specialist Physician in Boston, MA, registered under NPI 1861979833. NPPES records them as a sole proprietor, meaning the practice is not incorporated as a separate legal entity.
Getting there
The practice address on file is 300 LONGWOOD AVE # FEGAN4, Boston, MA 02115. We have not yet mapped what surrounds this office — parking, transit, and nearby pharmacies are added as our data collection reaches each location.
Credentials and Medicare
| Licence | State | Specialty |
|---|---|---|
| 277567 | MA | Pediatric Ophthalmology and Strabismus… primary |
This provider holds licence 277567 issued in MA. A licence number in NPPES reflects what was filed at registration — it does not confirm the licence is still active today.
This NPI does not appear in the PECOS Medicare enrolment file. Providers who do not bill Medicare — or who bill only through a group's enrolment — will not appear here. It is not a sign of any problem with the registration.
What Pediatric Ophthalmology and Strabismus Specialist covers
An ophthalmologist who specializes in pediatric ophthalmology and strabismus management. The subspecialty includes the medical and surgical management of eye disorders found in children. Some of the more common disorders include amblyopia, strabismus, refractive error, cataract and glaucoma. These disorders may be related to neurological and endocrinological diseases, trauma, or aging changes in the extraocular muscles requiring medical, optical and surgical management. NUCC Health Care Provider Taxonomy, code 207WX0110X
The taxonomy records how the provider classifies their own practice. It does not confirm which conditions they currently treat, whether they are accepting new patients, or which insurance they take — call the office for that.
Full NPPES record
An NPI-1 identifies a single person. It stays with the clinician for life, even if they move practice or change state, which is why the address on file can lag behind where they actually work today.
| NPI | 1861979833 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Jul 23, 2018 |
| Last updated | Feb 1, 2019 |
| Status | Active |
| Sole proprietor | Yes |
| Practice address |
300 LONGWOOD AVE # FEGAN4 Boston, MA 02115 (857) 472-2148 |
Number check
How the check works, step by step
Every NPI carries a Luhn check digit — the same scheme used on credit cards. CMS prefixes the number with 80840 before computing it, which marks it as a US health identifier.
| Digit | 8 | 0 | 8 | 4 | 0 | 1 | 8 | 6 | 1 | 9 | 7 | 9 | 8 | 3 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 8 | 3 | 1 | 9 | 7 | 9 | 8 | 6 |
Sum = 77 · next multiple of 10 = 80 · check digit = 3 · actual last digit = 3
A valid check digit only means the number is well-formed. It does not mean the provider is licensed, active, or in good standing — those are separate questions answered by the sections above.