ICD-10 Code H51.23 – Internuclear Ophthalmoplegia, Bilateral (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code H51.23 – Internuclear ophthalmoplegia, bilateral
What it is
H51.23 identifies bilateral internuclear ophthalmoplegia, a disorder of horizontal eye movement caused by dysfunction in the brainstem pathways that coordinate both eyes. It describes the condition itself, not the underlying cause.
Clinical signs
Typical findings include impaired adduction of both eyes, with outward movement of the abducting eye and possible nystagmus on lateral gaze. Clinical features vary; refer to documentation.
When to use this code
Use H51.23 when the record clearly documents bilateral internuclear ophthalmoplegia or bilateral INO. Apply it when the diagnosis is confirmed by a clinician and is the reason for evaluation, observation, or follow-up. Check documentation if the note only describes diplopia or a brainstem lesion without naming INO.
Do not use for
Do not use this code for unilateral internuclear ophthalmoplegia, nonspecific ocular motor palsy, or general diplopia without a documented diagnosis. If the provider documents only suspected INO, code the confirmed condition instead.
Coding tip
Code the documented laterality exactly; bilateral INO is not the same as unilateral or unspecified ocular motility disorder.