ICD-10 Code H21.331 – Parasitic cyst of iris, ciliary body or anterior chamber, right eye (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H21.331 – Parasitic cyst of iris, ciliary body or anterior chamber, right eye
What it is
This code identifies a parasitic cyst located in the iris, ciliary body, or anterior chamber of the right eye. Use it when documentation specifies the right eye and a parasitic origin.
Clinical signs
Findings may include a visible cyst or mass in the anterior segment, eye irritation, redness, blurred vision, or light sensitivity. Clinical features vary; refer to documentation.
When to use this code
Use H21.331 when the provider documents a parasitic cyst affecting the iris, ciliary body, or anterior chamber of the right eye. It may also apply when imaging or examination confirms the lesion and the laterality is clearly stated. Check documentation if the eye or parasitic cause is not specified.
Do not use for
Do not use this code for nonparasitic cysts, unspecified ocular cysts, or lesions in another eye. If the record does not confirm right-sided involvement, check documentation.
Coding tip
Verify both the anatomic site and right-eye laterality before assigning H21.331.