ICD-10 Code H21.56 – Pupillary abnormalities (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H21.56 – Pupillary abnormalities
What it is
H21.56 identifies abnormal findings involving the pupil, such as an unusual shape, size, or reaction to light. Use it when the chart documents a pupillary abnormality rather than a broader eye disease.
Clinical signs
Clinical features vary; refer to documentation. Commonly, the note may describe anisocoria, irregular pupil contour, or an abnormal pupillary response on exam.
When to use this code
Use this code when the clinician specifically documents a pupillary abnormality as the diagnosis or key finding. It may apply when the pupil is noted to be irregular, unequal, or otherwise abnormal without a more specific underlying condition being coded.
If the record identifies a cause, such as trauma or another eye disorder, code the documented condition instead of relying on this code alone. Check documentation for laterality, associated findings, and whether the abnormality is congenital or acquired.
Do not use for
Do not use this code for normal pupil variation or for symptoms only, if the provider does not document an abnormality. Do not use it when a more specific diagnosis explains the finding.
Coding tip
Assign H21.56 only when the abnormal pupil finding is clearly documented and not better captured by another diagnosis.