2026 ICD-10-CM Diagnosis Code H51.21Internuclear ophthalmoplegia, right eye

ICD-10-CM Codes›H00–H59›H49-H52›H51

ICD-10-CM H51.21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

H51.21 is a billable ICD-10-CM diagnosis code for internuclear ophthalmoplegia, right eye. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as dissociated gaze palsy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neuro-ophthalmology.

Code Identity

ICD-10-CM Code
H51.21
Billable Status
Yes — Valid for Submission
Code Describes
Internuclear ophthalmoplegia, right eye
Short Description
Internuclear ophthalmoplegia, right eye
Same as the full description in the CMS dataset.
Parent Code
H51.2
Internuclear ophthalmoplegia

Code Classification

ChapterH00–H59Diseases of the eye and adnexa
SectionH49-H52Disorders of ocular muscles, binocular movement, accommodation and refraction
CategoryH51Other disorders of binocular movement
This CodeH51.21Internuclear ophthalmoplegia, right eye

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Dissociated gaze palsy
  • Internuclear ophthalmoplegia
  • Internuclear ophthalmoplegia of right eye

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR EYE006
Neuro-ophthalmology
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Eye Movement Disorders

When you look at an object, you're using several muscles to move both eyes to focus on it. If you have a problem with the muscles, the eyes don't work properly.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert H51.21 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
378.86 Internucl ophthalmopleg
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About H51.21Overview

Is H51.21 (Internuclear ophthalmoplegia) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report internuclear ophthalmoplegia, right eye on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of H51.21?

Under the General Equivalence Mappings, internuclear ophthalmoplegia, right eye converts to ICD-9-CM 378.86 (internucl ophthalmopleg). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.