CPT® Code 99173

Last Updated: 2026 | Practical guidance aligned to CPT instructions, payer rebundling policies, and pediatric coding resources

Quick Reference

• What it is: A quantitative, bilateral visual acuity screening using graduated visual stimuli (typically an age-appropriate chart such as Snellen, Lea symbols, tumbling E). It is primarily used in pediatric preventive care to detect vision risk factors early.
• Separate reporting (CPT concept): Pediatric coding guidance explains that visual screening is considered a distinct service and may be reported in addition to a preventive medicine visit code when performed and documented.
• Bundling is payer-driven: Many payers treat 99173 as incidental or “rebundled” into the E/M or preventive service. UnitedHealthcare’s rebundling policy is a commonly cited example of the “not separately reimbursed” position.
• Never double-bill methods: Do not bill 99173 on the same date as instrument-based ocular screening (99174/99177). Vendor reimbursement guidance states 99173 should not be reported concurrently with instrument-based screening codes.
• Documentation must be numeric and bilateral: To support the code, document the test method and quantitative results for each eye (with/without correction). Pediatric coding guidance emphasizes that incomplete/unsuccessful screening generally should not be billed as 99173.
• Modifier strategy depends on payer edits: Many practices use modifier 25 on the preventive E/M when reporting 99173 on the same day; some Medicaid programs also provide specific instructions tied to NCCI-style bundling edits (for example, when and how to use modifiers to bypass edits).
• Know pediatric preventive coverage logic: UnitedHealthcare’s preventive care policy lists vision screening as a preventive service for children/adolescents (coverage as preventive does not guarantee separate reimbursement if the plan bundles payment).

CPT 99173 is used for a standardized visual acuity screening that produces a quantitative measurement (for example, 20/40) for each eye. In most practices, the screening occurs during well-child visits as part of routine preventive care, where early detection of amblyopia risk factors or refractive issues matters clinically. From a billing standpoint, 99173 is straightforward when the service is clearly performed and documented; the complexity comes from payer behavior—many insurers bundle the screening into the preventive visit payment, while others will pay a small additional amount or require specific modifier logic to bypass edits.

This guide focuses on practical, audit-ready workflows: when 99173 is appropriate, how to document it so it stands alone, how to link diagnoses correctly for preventive screening, how to avoid double-billing with instrument-based screening, and how to handle payer policies that “rebundle” or deny separate payment.

1. Code Definition & Appropriate Use

CPT 99173 represents a screening test of visual acuity that is quantitative and bilateral. Pediatric coding resources describe the typical office process as an eye-chart-based acuity screen performed on both eyes, appropriate to the child’s developmental level (letters, shapes, tumbling E, symbols). The essential attributes are:

• Screening purpose: The intention is screening—detecting possible problems in an otherwise preventive context, not diagnosing an established eye complaint.
• Quantitative output: The record should include numeric acuity (or the closest equivalent result from standardized symbols), not a qualitative statement like “vision okay.”
• Bilateral nature: The service is reported as a bilateral screen; you should document each eye’s result.

When the visit is primarily problem-based (for example, “blurred vision”), visual acuity testing is typically considered part of the evaluation rather than a separately billable screening. A payer or auditor reviewing the note will look at the reason for visit, assessment/plan language, and the presence of diagnostic eye work-up elements. As a best practice, reserve 99173 for routine preventive screening encounters and similar structured screening programs.

Practical threshold: If the service was not completed to the extent needed to produce reliable, documented bilateral results, many coding resources advise that you should not bill 99173 for that encounter. Document the attempt and the reason it could not be completed, then reattempt later or consider instrument-based screening when age-appropriate.

2. Documentation Standards (Audit-Proofing)

Documentation is the single most important factor for 99173 because it is frequently performed by clinical staff, takes little time, and can be incorrectly “assumed” as done during a preventive template. Pediatric coding guidance emphasizes that the note should support a distinct, billable screening service, including the method and results. A defensible documentation pattern includes the elements below.

Minimum required elements

• Method and distance: Identify the tool and testing conditions: “Snellen at 20 feet,” “Lea symbols at 10 feet,” or similar. If the practice uses a digital chart, name it and confirm it is a graduated acuity stimulus.
• Results by eye: Document right and left eye results separately (and optionally both eyes together). Example: “OD 20/40, OS 20/30, OU 20/30.”
• Correction status: Note whether the child wore glasses/contacts and whether the results are corrected or uncorrected (for example, “with correction” or “without correction”).
• Cooperation and limitations: If cooperation affects reliability, document it. If you cannot obtain reliable results, do not bill 99173 and record “unable to complete.” Pediatric coding guidance addresses the general principle that incomplete screening should not be billed as if performed.
• Plan for abnormal results: If failed, document follow-up: referral, rescreen interval, or additional evaluation pathway.

Examples of “pass” vs “fail” language

3. ICD-10 Linkage for Preventive vs Abnormal Findings

Diagnosis coding for 99173 should reflect screening rather than diagnosis of a symptomatic condition. The most typical linkage is the same preventive diagnosis used for the well visit (routine child health exam with or without abnormal findings). When the screening is abnormal, diagnosis selection should align with the chart narrative and the plan.

Common preventive linkages

• Routine well-child context: Link 99173 to the preventive diagnosis used for the encounter (for example, “routine child health examination without abnormal findings” vs “with abnormal findings”). Pediatric coding resources emphasize the concept that screenings may be separately reported when distinct and documented.
• Standalone screening encounter: If performed outside a comprehensive preventive visit (school form, program screening), use a screening-oriented diagnosis such as “encounter for screening for eye disorders” as appropriate for your documentation and program rules.
• Abnormal result handling: If the child fails screening, use the “with abnormal findings” preventive diagnosis and document what was abnormal. If you have a known refractive diagnosis already documented (or established in prior records), it can be added as a secondary diagnosis; otherwise, referral is often the appropriate next step.

In payer disputes, diagnosis coding often functions as a “preventive signal.” UnitedHealthcare’s preventive care policy describes vision screening as part of preventive services for children/adolescents. However, the same payer may still rebundle payment under a separate reimbursement policy. The practical lesson: correct diagnosis coding helps the claim route under preventive benefits, but does not guarantee separate payment if the payer’s payment policy bundles the code.

4. Payer Policies: Medicare, Medicaid, Commercial

Payer handling of 99173 typically falls into one of three categories: (1) covered as a preventive service and may pay separately, (2) covered but payment is bundled into the preventive visit, or (3) not covered or treated as incidental in most contexts. The same payer can describe coverage as preventive while still processing payment through rebundling logic.

Commercial payer example: rebundling into E/M

UnitedHealthcare’s professional rebundling policy is an explicit example of the “incidental/not separately reimbursed” approach. The policy describes situations where services are considered part of another billed service and therefore denied or adjusted. In practice, claims may show 99173 denied as inclusive even when performed and documented. This is not necessarily a coding error; it is a payment policy decision.

Commercial preventive policy example: preventive coverage concept

UnitedHealthcare’s preventive care services policy lists vision screening as part of preventive services for children/adolescents (plan and benefit design determine member cost-share). This is important for patient cost-sharing expectations. If a plan recognizes the service as preventive, the patient should not be cost-shared for the screening; whether the provider receives a separate line-item payment is a distinct issue governed by reimbursement policy.

Medicaid (EPSDT) workflow considerations

State Medicaid EPSDT programs often emphasize completion and documentation of age-appropriate screening. Some state guidance discusses how screening codes interact with edits and what modifier logic may be needed to avoid denial when billed with preventive visit codes. Medicaid practices should:

• Follow state periodicity schedules and required forms/workflows.
• Document results in a structured way (so you can produce them quickly for audits).
• Apply modifiers only when the state guidance or payer edits require them.

Plan-specific coding policy example

Some insurers publish coding/reimbursement policies stating that visual acuity screening is not separately reimbursed when performed with E/M services, reflecting the view that acuity assessment is integral to the visit. SelectHealth’s coding policy provides an example of that approach across plan types, clarifying when the code is treated as included/non-covered or not separately reimbursed.

Instrument screening coverage considerations

When the child is too young or uncooperative for chart-based testing, instrument-based ocular screening may be clinically preferable. Coverage for instrument screening can be age-limited or criteria-based. Aetna’s clinical policy bulletin on ocular photoscreening provides an example of how a payer frames medical necessity and age-related expectations for instrument screening. Even when instrument screening is used, the “do not double-bill methods” rule still applies.

flowchart TD
    A[Visual acuity screening performed?] -->|Yes| B[Bilateral quantitative results documented?]
    A -->|No / Incomplete| Z[Do NOT bill 99173]
    B -->|Yes| C[Instrument-based screening also performed?]
    B -->|No| Z
    C -->|Yes| D[Bill 99174/99177 only - never both]
    C -->|No| E[Check payer policy]
    E --> F{Payer rebundles 99173?}
    F -->|Yes - e.g. UHC| G[Bill 99173 but expect denial/bundling]
    F -->|No / Allows separate| H[Bill preventive E/M + 99173]
    H --> I{Payer edit requires modifier?}
    I -->|Yes| J[Add modifier 25 on E/M or 59/X on 99173 per payer rules]
    I -->|No| K[Submit without modifier]

5. Modifier Use: 25, 59/X{E,S,U}, and What Not to Use

Modifier use for 99173 is not about “making it payable” in a vacuum; it is about communicating to payer edits that the screening is a distinct service performed and documented during the encounter. The correct approach depends on how your payer edits are configured and whether a payer recognizes modifiers for this pair.

Modifier 25 on the preventive E/M

When a preventive visit and a minor procedure/test are billed on the same date, some payers expect modifier 25 on the E/M to indicate a significant, separately identifiable evaluation. Pediatric coding guidance addresses the practical reality that screenings often require modifier logic to bypass edits depending on payer behavior. If your payer denies 99173 as inclusive, adding modifier 25 may resolve an edit-driven denial—but it will not override a payer policy that explicitly rebundles 99173 into the visit fee.

Modifier 59 or X-modifiers on 99173 (payer-dependent)

Some state Medicaid guidance discusses NCCI-style edits between preventive visit codes and screening codes and indicates that a modifier may be allowed to bypass the edit when services are distinct and documented. In those systems, practices sometimes append modifier 59 (or an X-modifier when accepted) to 99173. Use this approach only when:

• The screening is actually performed and supported with bilateral quantitative results.
• The payer edit is known to be overrideable and the payer recognizes the modifier.
• Your internal policy is consistent (avoid scattershot modifier use that can attract audit scrutiny).

What not to use: reduced/discontinued service modifiers

Pediatric coding guidance emphasizes that when a child is uncooperative and the screening cannot be completed, the correct response is typically to not bill 99173 rather than trying to bill a partial service with reduced/discontinued procedure modifiers. The compliance risk is significant: billing a “completed screening code” without completed, documented results is a classic audit trigger.

6. Common Denial Triggers & Double-Billing Pitfalls

Most 99173 denials and compliance issues fall into a small number of categories. Building an internal checklist around these issues typically produces the fastest reduction in rework.

• No numeric results documented: A template checkbox is not enough; you need quantitative acuity outcomes per eye.
• Screening billed in a problem-focused eye complaint visit: Payers may view acuity as an inherent component of the E/M, consistent with plan coding policies that treat it as included.
• Concurrent billing with instrument-based screening: Vendor guidance states 99173 should not be billed concurrently with 99174/99177.
• Assuming “preventive coverage” equals “separate reimbursement”: Preventive policies can recognize the service as preventive while payment rules still rebundle it.
• Overuse of modifier 59: Some systems require it, but routine blanket use can raise questions. Apply only when justified and consistent with payer/state guidance.

7. Real-World Scenarios

Scenario 1: Well-child visit, normal screening

Patient: 5-year-old at annual preventive visit.

Screening: Snellen 20 ft: OD 20/30, OS 20/30 (uncorrected).

Coding approach: Preventive visit code + 99173 (as appropriate to payer rules). Consider modifier 25 on the preventive E/M if required by payer edits. Ensure documentation supports a distinct screening service.

Scenario 2: Well-child visit, failed screening with referral

Patient: 4-year-old at preventive visit.

Screening: Lea symbols 10 ft: OD 20/50, OS 20/40 (uncorrected).

Plan: Referral to optometry/ophthalmology documented.

Coding approach: Preventive visit diagnosis “with abnormal findings,” plus 99173 if the payer allows separate reporting. The referral plan supports the clinical significance of the abnormal screen and strengthens audit defensibility.

Scenario 3: Uncooperative 3-year-old, no reliable results

Patient: 3-year-old at preventive visit.

Screening attempt: Child will not occlude either eye; no reliable bilateral acuity obtained.

Coding approach: Do not bill 99173. Document “attempted, unable to complete,” and consider instrument-based screening workflow at a future visit if clinically appropriate.

Scenario 4: Instrument-based screening performed instead of chart

Patient: 2-year-old in a practice using photoscreening or automated devices.

Service: Instrument-based ocular screening performed successfully; chart screen not feasible.

Coding approach: Bill the appropriate instrument-based screening code (99174/99177) according to the method and interpretation workflow; do not also bill 99173. Vendor guidance explicitly cautions against concurrent billing of 99173 with instrument-based screening. Confirm payer criteria and age expectations (example: payer medical policy on photoscreening).

Scenario 5: Commercial payer rebundles 99173

Claim result: 99173 denied as inclusive/incidental when billed with preventive visit.

Interpretation: This can reflect payer rebundling policy rather than a coding error. UHC’s rebundling policy is a clear example of this payment logic even while preventive policy language may still recognize vision screening as preventive.

Next steps: If your contract/policy states bundling, write off and stop billing for that payer. If policy is unclear and you believe separate reimbursement is allowed, appeal with documentation showing distinct screening results and cite CPT-oriented screening guidance from pediatric coding resources.