Question 1

What is ICD-10 code H35.421?

Accepted Answer

H35.421 is the ICD-10-CM diagnosis code for microcystoid degeneration of retina, right eye. Small cyst-like formations in the outer edges of the right eye's retina that may affect vision. H35.421 sits in the ICD-10-CM chapter for diseases of the eye and adnexa (h00-h59), within the section covering disorders of choroid and retina (h30-h36).

H35.421 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 is documented; verify this is not a bilateral condition.

Question 2

Is H35.421 an HCC code?

Accepted Answer

No. H35.421 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 H35.421 billable?

Accepted Answer

Yes. H35.421 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. H35.421 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 H35.421?

Accepted Answer

H35.421 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 H35.421 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.

Question 5

What should coders know when reporting H35.421?

Accepted Answer

Confirm right eye laterality is documented; verify this is not a bilateral condition Document any associated vision changes or complications

HCC Buddy Code Card

H35.421

Is H35.421 an HCC code?

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Open H35.421 in the Interactive Encoder

H35.421 ICD-10-CM Code: Microcystoid degeneration of retina, right eye

HCC Buddy Code Card

H35.421

Is H35.421 an HCC code?

What This Code Means

Coding Tips

Child Codes

Code Hierarchy

Open H35.421 in the Interactive Encoder