ICD-10 Code H21.33 – Parasitic cyst of iris, ciliary body or anterior chamber (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H21.33 – Parasitic cyst of iris, ciliary body or anterior chamber
What it is
This code identifies a parasitic cyst located in the iris, ciliary body, or anterior chamber of the eye. Use it when documentation confirms a cyst caused by a parasitic infection in one of these anterior segment structures.
Clinical signs
Findings may include a visible cyst, anterior chamber inflammation, eye discomfort, redness, or blurred vision. Clinical features vary; refer to documentation and ophthalmic examination findings.
When to use this code
Use H21.33 when the provider documents a parasitic cyst specifically involving the iris, ciliary body, or anterior chamber. It may also apply when imaging or slit-lamp examination confirms the lesion and the note ties it to a parasitic cause. If the record only says “ocular cyst,” check documentation.
Do not use for
Do not use this code for nonparasitic cysts, generalized eye inflammation, or lesions in other parts of the eye. Check documentation if the site or parasitic etiology is unclear.
Coding tip
Code the anatomic site exactly as documented; laterality is not part of this code.