2026 ICD-10-CM Diagnosis Code H49.42Progressive external ophthalmoplegia, left eye

ICD-10-CM Codes›H00–H59›H49-H52›H49

ICD-10-CM H49.42
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

H49.42 is a billable ICD-10-CM diagnosis code for progressive external ophthalmoplegia, left eye. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as external ophthalmoplegia of left eye. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neuro-ophthalmology and Strabismus.

Code Identity

ICD-10-CM Code
H49.42
Billable Status
Yes — Valid for Submission
Code Describes
Progressive external ophthalmoplegia, left eye
Short Description
Progressive external ophthalmoplegia, left eye
Same as the full description in the CMS dataset.
Parent Code
H49.4
Progressive external ophthalmoplegia

Code Classification

ChapterH00–H59Diseases of the eye and adnexa
SectionH49-H52Disorders of ocular muscles, binocular movement, accommodation and refraction
CategoryH49Paralytic strabismus
This CodeH49.42Progressive external ophthalmoplegia, left eye

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • External ophthalmoplegia of left eye
  • Left progressive external ophthalmoplegia

Clinical ClassificationClinical

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

CCSR EYE006
Neuro-ophthalmology
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR EYE007
Strabismus
Default principal diagnosis: inpatient No · outpatient No

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 H49.42 to ICD-9-CMHistory

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

ICD-9-CM
378.55 External ophthalmoplegia
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 H49.42Overview

Is H49.42 (Progressive external ophthalmoplegia) a billable code?

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

What is the ICD-9 equivalent of H49.42?

Under the General Equivalence Mappings, progressive external ophthalmoplegia, left eye converts to ICD-9-CM 378.55 (external ophthalmoplegia). 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.