ICD-10 Code H18.621 – Keratoconus, unstable, right eye (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H18.621 – Keratoconus, unstable, right eye
What it is
This code identifies keratoconus in the right eye when the corneal shape is actively changing or unstable. It tells you the condition is limited to the right eye and is not described as stable.
Clinical signs
Typical findings include progressive corneal thinning, irregular astigmatism, and reduced or distorted vision. Clinical features vary; refer to documentation for evidence of instability or progression in the right eye.
When to use this code
Use H18.621 when the provider documents unstable keratoconus affecting only the right eye. This fits notes describing progression, worsening refraction, or corneal changes over time. If the record does not clearly state instability, check documentation before assigning this code.
Do not use for
Do not use this code for stable keratoconus, left eye disease, bilateral disease, or nonspecific corneal thinning. If the chart does not confirm right-eye instability, check documentation.
Coding tip
Match the laterality and stability exactly as documented; both are required for accurate code selection.