2027 ICD-10-CM Diagnosis Code H55.00Unspecified nystagmus

ICD-10-CM Codes›H00–H59›H55-H57›H55

ICD-10-CM H55.00
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

H55.00 is a billable ICD-10-CM diagnosis code for unspecified nystagmus. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 123. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified eye disorders.

Code Identity

ICD-10-CM Code
H55.00
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified nystagmus
Short Description
Unspecified nystagmus
Same as the full description in the CMS dataset.
Parent Code
H55.0
Nystagmus

Code Classification

ChapterH00–H59Diseases of the eye and adnexa
SectionH55-H57Other disorders of eye and adnexa
CategoryH55Nystagmus and other irregular eye movements
This CodeH55.00Unspecified nystagmus

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired nystagmus
  • Essential tremor
  • Eyelid nystagmus
  • Hereditary essential tremor
  • Idiopathic nystagmus
  • Irregular nystagmus
  • Manifest nystagmus
  • Nystagmus
  • Nystagmus and other irregular eye movements
  • Nystagmus inhibited when fixation removed
  • Nystagmus present
  • Nystagmus unchanged when fixation removed
  • Permanent nystagmus
  • Physiological nystagmus
  • Rotational nystagmus
  • Tremor, nystagmus, duodenal ulcer syndrome
  • Uniocular nystagmus
  • Uniocular nystagmus of left eye
  • Uniocular nystagmus of right eye

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to H55.00: its own notes plus those printed at Chapter 7. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 7 (H00-H59) Diseases of the eye and adnexa applies to 2,677 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • diabetes mellitus related eye conditions (E09.3-, E10.3-, E11.3-, E13.3-)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury (trauma) of eye and orbit (S05.-)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • syphilis related eye disorders (A50.01, A50.3-, A51.43, A52.71)

Notes

General instructions on how these codes are used.

From Chapter 7 (H00-H59) Diseases of the eye and adnexa applies to 2,677 codes
  • Use an external cause code following the code for the eye condition, if applicable, to identify the cause of the eye condition

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name H55.00, its category, or a range that includes it.

Applicable To 1

These notes mention H55.00.

  • Z83.51 Family history of eye disorders
    Conditions classifiable to H00-H53, H55-H59 names H55-H59, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming H55.00: its condition is not part of those codes, and both may be reported when the patient has both.

  • Block H49-H52 Disorders of ocular muscles, binocular movement, accommodation and refraction
    nystagmus and other irregular eye movements (H55) names H55, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR EYE012
Other specified eye disorders
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 H55.00 to ICD-9-CMHistory

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

ICD-9-CM
379.50 Nystagmus 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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About H55.00Overview

What is the ICD-10 code for unspecified nystagmus?

The ICD-10-CM code for unspecified nystagmus is H55.00 (sometimes written as H5500). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is H55.00 (Nystagmus) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified nystagmus on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does H55.00 group to?

When unspecified nystagmus is the principal diagnosis on an inpatient stay, it groups to MS-DRG 123 (neurological Eye Disorders), which carries a relative weight of 0.8218. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of H55.00?

Under the General Equivalence Mappings, unspecified nystagmus converts to ICD-9-CM 379.50 (nystagmus NOS). The mapping is a direct match.