Question 1

What is ICD-10 code H21.301?

Accepted Answer

H21.301 is the ICD-10-CM diagnosis code for idiopathic cysts of iris, ciliary body or anterior chamber, right eye. Fluid-filled cysts in the iris, ciliary body, or front chamber of the right eye that develop without a known cause. H21.301 sits in the ICD-10-CM chapter for diseases of the eye and adnexa (h00-h59), within the section covering disorders of sclera, cornea, iris and ciliary body (h15-h22).

H21.301 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.

Confirm right eye laterality and that cysts are idiopathic (not secondary to trauma or disease).

Question 2

Is H21.301 an HCC code?

Accepted Answer

No. H21.301 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is H21.301 billable?

Accepted Answer

Yes. H21.301 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. H21.301 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.

Question 4

What is the V28 vs V24 difference for H21.301?

Accepted Answer

H21.301 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 community model rewards H21.301 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's V28/V24 community RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a community payment HCC.

Question 5

What should coders know when reporting H21.301?

Accepted Answer

Confirm right eye laterality and that cysts are idiopathic (not secondary to trauma or disease) Document the specific location of cysts (iris, ciliary body, or anterior chamber) when available

HCC Buddy Code Card

H21.301

Is H21.301 an HCC code?

Get the V28 RAF + MEAT cheat sheet

What This Code Means

Coding Tips

Child Codes

Code Hierarchy

Work H21.301 in HCC Buddy

H21.301 ICD-10-CM Code: Idiopathic cysts of iris, ciliary body or anterior chamber, right eye

HCC Buddy Code Card

H21.301

Is H21.301 an HCC code?

Get the V28 RAF + MEAT cheat sheet

What This Code Means

Coding Tips

Child Codes

Code Hierarchy

Work H21.301 in HCC Buddy