What is ICD-10 code H40.831?

H40.831 is the ICD-10-CM diagnosis code for Aqueous misdirection, right eye. A type of glaucoma in the right eye where the eye's fluid (aqueous humor) is being directed or flowing abnormally, causing increased eye pressure and potential vision problems. H40.831 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. H40.831 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. H40.831 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. H40.831 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for H40.831?

H40.831 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards H40.831 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

What should coders know when reporting H40.831?

Document the specific mechanism of misdirection (e.g., pupillary block, ciliary block) if available in the clinical record Distinguish from other secondary glaucomas by confirming aqueous misdirection is the primary pathophysiology

H40.831: Aqueous misdirection, right eye — ICD-10

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupH40.831Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the eye and adnexa (H00-H59) / Glaucoma (H40-H42)

H40.831

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Aqueous misdirection, right eye

A type of glaucoma in the right eye where the eye's fluid (aqueous humor) is being directed or flowing abnormally, causing increased eye pressure and potential vision problems.

Buddy Insight

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Not risk-adjusted for this model/period.

RAF 0

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Not risk-adjusted for this model/period.

RAF 0

RXHCC

Mapped

HCC 244

Glaucoma, Other

RAF 0.0

Code Trumping

Basket needed

Compare selected patient codes to show trumped or trumps impact.

Code Book Path

Official

H40.8Other glaucoma

H40.83Aqueous misdirection

H40.831Aqueous misdirection, right eye

Inclusion Terms

Official

Malignant glaucoma

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for H40.831 in this effective period.

Related Child Codes

Official

H40.832Aqueous misdirection, left eye

H40.833Aqueous misdirection, bilateral

H40.839Aqueous misdirection, unspecified eye

Includes

Official

ICD-10-CM does not list Includes notes for H40.831 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for H40.831 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for H40.831 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for H40.831 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for H40.831 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Laterality clearly specified as right eye

Clinical or imaging evidence of posterior aqueous misdirection (shallow or flat anterior chamber with elevated intraocular pressure)

Intraocular pressure measurement

History of precipitating event if applicable (e.g., recent intraocular surgery, laser treatment)

MEAT Support

HCC Buddy guidance

Laterality clearly specified as right eye

Clinical or imaging evidence of posterior aqueous misdirection (shallow or flat anterior chamber with elevated intraocular pressure)

Intraocular pressure measurement

History of precipitating event if applicable (e.g., recent intraocular surgery, laser treatment)

Audit Caution

HCC Buddy guidance

Confusing aqueous misdirection with acute angle-closure glaucoma — both present with elevated IOP and shallow anterior chamber but have different mechanisms

Failing to distinguish from suprachoroidal hemorrhage or effusion, which can mimic aqueous misdirection

Not documenting the relationship to prior surgery when applicable, which is important for accurate clinical context

Using a generic secondary glaucoma code when the specific diagnosis of aqueous misdirection is documented

Common Mistakes

HCC Buddy guidance

H40.211-H40.219 — Acute angle-closure glaucoma (different mechanism; pupillary block vs. ciliary block)

H40.821-H40.829 — Hypersecretion glaucoma (overproduction of aqueous, not misdirection)

H40.50-H40.53 — Secondary glaucoma due to other eye diseases (less specific than aqueous misdirection)

H59.011-H59.019 — Postprocedural vitreous syndrome (related but different complication)

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is H40.831 an HCC code?

No. H40.831 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

HCC Category Mapping

RxHCCHCC 244, Glaucoma, Other

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work H40.831 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for H40.831

For H40.831to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed H40.831 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

Get the V28 RAF + MEAT cheat sheet

One printable page: confirm a code's V28 HCC status, its RAF weight, and the MEAT your note needs to make it stick. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

H40.831 is the ICD-10-CM diagnosis code for aqueous misdirection, right eye. A type of glaucoma in the right eye where the eye's fluid (aqueous humor) is being directed or flowing abnormally, causing increased eye pressure and potential vision problems. H40.831 sits in the ICD-10-CM chapter for diseases of the eye and adnexa (h00-h59), within the section covering glaucoma (h40-h42).

H40.831 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

Maps to RxHCC 244 (Glaucoma, Other) with a RAF weight of 0.000 in the prescription drug model. No mapping under CMS-HCC v28, v24, or ESRD models. Despite the clinical severity of aqueous misdirection, its risk adjustment impact is limited to the prescription drug model. No hierarchies apply.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for H40.831 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Document the specific mechanism of misdirection (e.g., pupillary block, ciliary block) if available in the clinical record
•Distinguish from other secondary glaucomas by confirming aqueous misdirection is the primary pathophysiology

Clinical Significance

Aqueous misdirection, also known as malignant glaucoma or ciliary block glaucoma, is a serious condition where aqueous humor is misdirected posteriorly into the vitreous cavity rather than flowing anteriorly through the pupil. This creates a dangerous cycle of rising intraocular pressure that can be refractory to standard glaucoma treatments. It often occurs after intraocular surgery and requires urgent intervention.

Documentation Requirements

✓Laterality clearly specified as right eye
✓Clinical or imaging evidence of posterior aqueous misdirection (shallow or flat anterior chamber with elevated intraocular pressure)
✓Intraocular pressure measurement
✓History of precipitating event if applicable (e.g., recent intraocular surgery, laser treatment)
✓Anterior segment examination findings including anterior chamber depth
✓B-scan ultrasound or anterior segment optical coherence tomography results if performed
✓Treatment approach documented (medical, laser, or surgical intervention)

Commonly Confused Codes

•H40.211-H40.219: Acute angle-closure glaucoma (different mechanism; pupillary block vs. ciliary block)
•H40.821-H40.829: Hypersecretion glaucoma (overproduction of aqueous, not misdirection)
•H40.50-H40.53: Secondary glaucoma due to other eye diseases (less specific than aqueous misdirection)
•H59.011-H59.019: Postprocedural vitreous syndrome (related but different complication)