ICD-10 Code H21.301 – Idiopathic cysts of iris, ciliary body or anterior chamber, right eye (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H21.301 – Idiopathic cysts of iris, ciliary body or anterior chamber, right eye
What it is
This code identifies an idiopathic cyst affecting the iris, ciliary body, or anterior chamber in the right eye. “Idiopathic” means the cause is not documented or not known.
Clinical signs
Findings may include a visible cyst on eye examination, a localized anterior segment mass, or incidental discovery during slit-lamp evaluation. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents a cyst of the iris, ciliary body, or anterior chamber in the right eye and no specific cause is identified. It is also appropriate when the record clearly states idiopathic or unexplained. If the location or laterality is unclear, check documentation before coding.
Do not use for
Do not use this code for cysts with a documented cause, such as trauma, surgery, or infection. Do not assign it if the cyst is in the left eye, bilateral, or the site is not specified.
Coding tip
Confirm both laterality and the idiopathic nature in the ophthalmology note before assigning H21.301.