2026 ICD-10-CM Diagnosis Code H33.121Parasitic cyst of retina, right eye

ICD-10-CM Codes›H00–H59›H30-H36›H33

ICD-10-CM H33.121
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

H33.121 is a billable ICD-10-CM diagnosis code for parasitic cyst of retina, right eye. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 121 through 122. Coders also document this condition as parasitic cyst of retina. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Retinal and vitreous conditions.

Code Identity

ICD-10-CM Code
H33.121
Billable Status
Yes — Valid for Submission
Code Describes
Parasitic cyst of retina, right eye
Short Description
Parasitic cyst of retina, right eye
Same as the full description in the CMS dataset.
Parent Code
H33.12
Parasitic cyst of retina

Code Classification

ChapterH00–H59Diseases of the eye and adnexa
SectionH30-H36Disorders of choroid and retina
CategoryH33Retinal detachments and breaks
This CodeH33.121Parasitic cyst of retina, right eye

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Parasitic cyst of retina
  • Right parasitic retinal cyst

Clinical ClassificationClinical

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

CCSR EYE005
Retinal and vitreous conditions
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Parasitic Diseases

Parasites are living things that use other living things - like your body - for food and a place to live. You can get them from contaminated food or water, a bug bite, or sexual contact. Some parasitic diseases are easily treated and some are not.

Read the full article at MedlinePlus

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

Convert H33.121 to ICD-9-CMHistory

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

ICD-9-CM
360.13 Parasitic endophthal NOS
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 H33.121Overview

Is H33.121 (Parasitic cyst of retina) a billable code?

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

What MS-DRG does H33.121 group to?

When parasitic cyst of retina, right eye is the principal diagnosis on an inpatient stay, it groups to MS-DRG 121, 122, with relative weights from 0.7858 to 1.1633 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of H33.121?

Under the General Equivalence Mappings, parasitic cyst of retina, right eye converts to ICD-9-CM 360.13 (parasitic endophthal NOS). 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.