ICD-10 Code H21.309 – Idiopathic cysts of iris, ciliary body or anterior chamber, unspecified eye (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H21.309 – Idiopathic cysts of iris, ciliary body or anterior chamber, unspecified eye
What it is
This code identifies an unspecified eye cyst involving the iris, ciliary body, or anterior chamber when the cause is not known. Use it when the record documents an idiopathic cyst but does not specify the exact ocular structure.
Clinical signs
Clinical features vary; refer to documentation. These cysts may be noted on eye examination or imaging as a cystic lesion in the anterior segment, sometimes without symptoms.
When to use this code
Use H21.309 when the provider documents an idiopathic cyst of the iris, ciliary body, or anterior chamber and laterality is not specified. It also fits when the note confirms a cystic lesion in this region but does not name a more specific diagnosis.
Choose this code only when documentation supports an idiopathic cause and no more specific eye code is available. Check the chart for laterality, exact anatomic site, and whether another condition explains the finding.
Do not use for
Do not use this code for traumatic, inflammatory, parasitic, or neoplastic cysts. If the cyst is better described by another specified ocular disorder, code that condition instead.
Coding tip
Verify both the cause and the eye laterality in the ophthalmology note before assigning an unspecified code.