CPT code 66179: Glaucoma shunt, without graft2026 Medicare rate & RVUs in California

CMS doesn’t publish an office rate for 66179 in California.

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

What 66179 covers

An ophthalmic surgeon places a drainage tube connected to a plate reservoir outside the eye to redirect aqueous fluid and reduce intraocular pressure. This operation is used for glaucoma when pressure control requires a drainage implant; it is commonly performed in a hospital outpatient department or ambulatory surgery center. The coded service is the shunt placement without a graft, distinguishing it from placement that includes a graft.

Select the code when the operative report supports placement of an aqueous shunt to an extraocular reservoir and confirms that no graft was used. The major-surgery global period includes the day-before preoperative visit and 90 days of related postoperative care. When multiple procedures are performed in the same session, the highest-valued procedure is paid in full and other procedures are subject to the standard 50% reduction. For bilateral surgery, modifier 50 is paid at 150%. An assistant at surgery may be paid; co-surgeons and team surgery are not permitted.

This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.

Where 66179 pays more and less in California

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

29 of 29 payment localities

How the 66179 rate is calculated

Each of 66179’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.

Payment rules and modifiers for 66179

66179 has a 90-day global period: related visits in that window are included in the surgery payment.

What modifiers do to the payment

When to use modifier 50

66179 compared with similar codes

How to choose

66180Glaucoma shuntWith graft

The procedures both place a shunt to an extraocular reservoir. The distinguishing feature is whether a graft is used.

66183Drainage deviceWithout extraocular reservoir

Use 66183 for an anterior-segment drainage device without an extraocular reservoir; this code involves a shunt connected to an extraocular reservoir.

66170TrabeculectomyWithout prior scarring

66170 is a different glaucoma operation. Choose this code when the documented procedure places an aqueous shunt to an extraocular reservoir without a graft.

66184Shunt revisionWithout graft

66184 describes revision of an existing aqueous shunt, not placement of a new shunt.

Codes related to 66179

Related codes aren’t interchangeable: bill the code that matches the service performed.

Where these rates come from

FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.

CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027

Open CMS sourceHow we calculate rates