ICD-10 Code H52.21 – Irregular astigmatism (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H52.21 – Irregular astigmatism
What it is
Irregular astigmatism is a refractive error caused by uneven curvature of the cornea or lens, so light does not focus to one clear point. You use this code when the chart documents irregular, not regular, astigmatism.
Clinical signs
Patients often report blurred or distorted vision that may not improve fully with standard glasses. Clinical features vary; refer to documentation for corneal irregularity, poor visual quality, or findings on refraction and corneal examination.
When to use this code
Use H52.21 when the provider specifically diagnoses irregular astigmatism, including cases noted during eye exams or refractive evaluations. It may also apply when the record describes corneal surface irregularity causing distorted refraction. Check documentation if the cause is linked to another eye disorder.
Do not use for
Do not use this code for regular astigmatism, simple blurred vision, or unspecified refractive error. If the note does not clearly identify irregular astigmatism, check documentation before coding.
Coding tip
Code the documented diagnosis only; if the record names an underlying corneal condition, verify whether an additional code is needed.