ICD-10 Code H40.21 – Acute angle-closure glaucoma (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H40.21 – Acute angle-closure glaucoma
What it is
H40.21 identifies acute angle-closure glaucoma, a sudden rise in eye pressure caused by blocked fluid drainage. Use it when the record specifically documents an acute angle-closure episode.
Clinical signs
Typical findings include severe eye pain, blurred vision, halos around lights, red eye, headache, nausea, and a mid-dilated pupil. Clinical features vary; refer to documentation.
When to use this code
Use H40.21 when the provider documents acute angle-closure glaucoma or an acute angle-closure attack. It fits emergency ophthalmology notes, discharge summaries, and specialist assessments that clearly name the condition. Check documentation if the record only says glaucoma or eye pain.
Do not use for
Do not use this code for chronic open-angle glaucoma, unspecified glaucoma, or suspected glaucoma without confirmation. Also avoid it when the note describes a history of glaucoma without an acute episode.
Coding tip
Confirm the documentation says “acute angle-closure” rather than just “glaucoma” before assigning H40.21.