Medically Unlikely Edits in Retina Coding

Accurate coding for retina procedures requires more than selecting the correct Current Procedural Terminology (CPT) and Healthcare Common Procedure Coding System (HCPCS) codes. Medically Unlikely Edits (MUEs) play a critical role in determining how many units of a service may be reported and paid on a single date of service. When MUE requirements are not followed, claims may be denied or underpaid—even if the services reported are medically necessary and well-documented.

WHAT ARE MEDICAL UNLIKELY EDITS?

MUEs are established by the CMS and updated quarterly. An MUE for a CPT or HCPCS code is the maximum units of service that a provider would report under most circumstances for a single patient on a single date of service.¹ Not every CPT code has an assigned MUE; however, if an MUE exists, it must be followed, as claims submitted with units exceeding the MUE will be denied. Think of it like an ATM that allows only one withdrawal per day—even if you feel justified that an additional withdrawal is warranted, the system can process only one transaction. The most current MUEs can be found on the CMS website² or in the AAO’s Ophthalmic Coding Coach.

MUEs apply to both unilateral and bilateral services, in most instances. Many commonly reported retina services, including examinations, diagnostic testing, and both minor and major procedures, will have an MUE of 1. Examples include evaluation and management services, OCT imaging, fundus photography, intravitreal injection, retinal photocoagulation, and vitrectomy procedures. Because these services are limited to a single payable unit per day, understanding the assigned MUE is essential before claim submission.

Procedure Codes Versus Drug Codes

While most retina CPT codes are limited to 1 payable unit per eye per day (ie, MUE of 1), HCPCS drug codes are different. MUEs for drug codes are typically set high enough to accommodate bilateral dosing when medically necessary, often allowing double the per-eye number of billing units. Examples of MUEs for HCPCS drug codes include:

• J2778 (ranibizumab 0.3 mg or 0.5 mg [Lucentis, Genentech/Roche]) has an MUE of 10 units
• J0178 (aflibercept 2 mg [Eylea, Regeneron]) has an MUE of 4 units
• J0177 (aflibercept 8 mg [Eylea HD, Regeneron]) has an MUE of 16 units
• J2781 (pegcetacoplan 15 mg [Syfovre, Apellis]) has an MUE of 30 units

This distinction is critical: While drug MUEs are designed to support bilateral treatment and reimbursement, the injection procedure itself is subject to billing only 1 unit.

Bilateral Indicators

It is important to distinguish MUEs from bilateral indicators. Bilateral indicators define how a payer calculates payment when a procedure is performed on each eye during the same session. Returning to the ATM analogy, MUEs determine how many times a withdrawal is allowed per day, while bilateral indicators determine how that approved amount is distributed. If the billed units on a claim exceed the MUE without a bilateral modifier, it is stopped at the first checkpoint, and the bilateral payment rules are never applied. However, if a bilateral procedure is performed, the indicators must be considered to determine if modifiers are appropriate (eg, modifier -50, -RT, -LT).³

CPT 67028: A Common Coding Challenge

When intravitreal injections are medically necessary in each eye on the same date of service, coding confusion is common. Although CPT code 67028 is limited to 1 payable unit per date of service due to its MUE, the bilateral indicator is 1, which allows for a 150% payment. Some payers allow the bilateral service to be reported on a single line with modifier -50, 1 unit, and a doubled fee, in accordance with their bilateral billing guidelines and indicator.

Treating Wet and Dry AMD in the Same Eye

Patients with geographic atrophy (GA) may also have wet AMD in the same eye, requiring concurrent treatment with anti-VEGF therapy. When both conditions are treated during the same visit, two separate intravitreal injections may be clinically appropriate in the same eye, but only 1 unit of CPT 67028 will be reimbursed.⁴ In these cases, accurate diagnosis-to-code linking on the CMS-1500 claim form (or electronic equivalent) is essential. Practices should:

• link both the wet and dry AMD ICD-10 codes to CPT 67028,
• link only the wet AMD ICD-10 code to the HCPCS code for the anti-VEGF medication, and
• link only the dry AMD ICD-10 code to the HCPCS code for the GA medication.

Although payment is limited to a single injection code per eye, proper diagnosis linking supports medical necessity for both drugs and helps reduce denials related to diagnosis mismatches.

Bilateral Surgery

Although bilateral surgery is uncommon in retina practice, it does occur and requires careful attention to MUEs. CPT 67210 (focal laser photocoagulation for wet AMD) has an MUE of 1, same eye, same session. When performed on both eyes during the same session, Medicare Part B requires the bilateral service to be reported as a single line item with 1 unit, per the MUEs.

Since April 1, 2013, CMS policy has required this submission format for Medicare bilateral surgeries subject to an MUE of 1.⁵ When reported correctly, Medicare applies the bilateral payment methodology, reimbursing 100% of the allowable for the first eye and 50% for the second eye. Commercial payer requirements may differ, and payer-specific guidelines should always be verified.

If bilateral surgery is incorrectly reported with multiple units or separate line items without a bilateral modifier, the payer may pay for only one eye, deny the additional unit, or fail to apply the bilateral payment adjustment. These automated edits occur even before documentation is reviewed, which can lead to underpayment or denial despite clearly documented bilateral surgery.

KEY TAKEAWAY

When an MUE exists, exceeding the allowable units will result in denial, regardless of medical necessity or documentation. As retinal therapies become more complex, understanding and applying MUE rules remains essential for accurate coding and timely reimbursement.

1. Medically Unlikely Edits. Palmetto GPA. Accessed January 12, 2026. palmettogba.com/jjb/admin/tools/mue

2. Medicare NCCI Medically Unlikely Edits (MUEs). CMS.gov. Accessed January 12, 2026. www.cms.gov/medicare/coding-billing/national-correct-coding-initiative-ncci-edits/medicare-ncci-medically-unlikely-edits-mues

3. Woodke J. The effect of bilateral rules on retina coding. Retina Today. 2024;7(4):5.

4. Shah AR, Woodke J. Geographic atrophy—how to get paid for new treatments. American Academy of Ophthalmology. November 1, 2023. Accesses January 14, 2025. www.aao.org/eyenet/article/geographic-atrophy-how-to-get-paid-new-treatments

5. CMS Manual System. Department of Health & Human Services. August 15, 2014. Accessed January 22, 2026. www.cms.gov/regulations-and-guidance/guidance/transmittals/downloads/r1421otn.pdf