2026 ICD-10-CM Diagnosis Code H18.40Unspecified corneal degeneration

ICD-10-CM Codes›H00–H59›H15-H22›H18

ICD-10-CM H18.40
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

H18.40 is a billable ICD-10-CM diagnosis code for unspecified corneal degeneration. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 124 through 125. Coders also document this condition as corneal degeneration. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Cornea and external disease.

Code Identity

ICD-10-CM Code
H18.40
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified corneal degeneration
Short Description
Unspecified corneal degeneration
Same as the full description in the CMS dataset.
Parent Code
H18.4
Corneal degeneration

Code Classification

ChapterH00–H59Diseases of the eye and adnexa
SectionH15-H22Disorders of sclera, cornea, iris and ciliary body
CategoryH18Other disorders of cornea
This CodeH18.40Unspecified corneal degeneration

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Corneal degeneration
  • Corneal epithelial degeneration
  • Corneal stromal degeneration
  • Degeneration of cornea of bilateral eyes
  • Degeneration of cornea of left eye
  • Degeneration of cornea of right eye

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Degeneration, degenerative
      • cornea

Clinical ClassificationClinical

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

CCSR EYE001
Cornea and external disease
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Corneal Disorders

Your cornea is the outermost layer of your eye. It is clear and shaped like a dome. The cornea helps to shield the rest of the eye from germs, dust, and other harmful matter. It also helps your eye to focus. If you wear contact lenses, they float on top of your corneas.

Read the full article at MedlinePlus

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

Convert H18.40 to ICD-9-CMHistory

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

ICD-9-CM
371.40 Corneal degeneration NOS
Exact Match The mapping is direct, with no qualifiers.

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 H18.40Overview

Is H18.40 (Corneal degeneration) a billable code?

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

What MS-DRG does H18.40 group to?

When unspecified corneal degeneration is the principal diagnosis on an inpatient stay, it groups to MS-DRG 124, 125, with relative weights from 0.7678 to 1.3231 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of H18.40?

Under the General Equivalence Mappings, unspecified corneal degeneration converts to ICD-9-CM 371.40 (corneal degeneration NOS). The mapping is a direct match.

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.