2026 ICD-10-CM Diagnosis Code H42

Approximate Synonyms

The following list of clinical terms are approximate synonyms, alternative descriptions, or common phrases that might be used by patients, healthcare providers, or medical coders to describe the same condition. These synonyms and related diagnosis terms are often used when searching for an ICD-10 code, especially when the exact medical terminology is unclear. Whether you're looking for lay terms, similar diagnosis names, or common language alternatives, this list can help guide you to the correct ICD-10 classification.

Clinical Classification

Clinical Classifications group individual ICD-10-CM diagnosis codes into broader, clinically meaningful categories. These categories help simplify complex data by organizing related conditions under common clinical themes.

They are especially useful for data analysis, reporting, and clinical decision-making. Even when diagnosis codes differ, similar conditions can be grouped together based on their clinical relevance. Each category is assigned a unique CCSR code that represents a specific clinical concept, often tied to a body system or medical specialty.

Code Edits

The Medicare Code Editor (MCE) detects errors and inconsistencies in ICD-10-CM diagnosis coding that can affect Medicare claim validity. These Medicare code edits help medical coders and billing professionals determine when a diagnosis code is not appropriate as a principal diagnosis, does not meet coverage criteria. Use this list to verify whether a code is valid for Medicare billing and to avoid claim rejections or denials due to diagnosis coding issues.

MS-DRG Mapping for ICD-10-CM Code H42

Diagnosis-Related Groups (DRGs) are used to classify hospital cases for billing and healthcare management. They help standardize how hospitals and other providers are reimbursed for inpatient care. Patients are grouped based on their principal diagnosis into broader categories called Major Diagnostic Categories (MDCs).

Once assigned to a DRG, the hospital receives a set payment for the patient’s care, regardless of the actual services provided. This fixed rate is intended to cover the typical cost of treating patients within that group. The payment amount depends on the DRG's relative weight, which reflects the expected complexity and cost of care based on the severity of the patient’s condition.

Diagnostic related groups encourage healthcare providers to focus on quality and efficiency in patient care while managing costs effectively. The diagnosis code is present in the following groups for version MS-DRG V43.0 applicable from 10/01/2025 through 09/30/2026.

Convert H42 to ICD-9-CM

Below are the ICD-9 codes that most closely match this ICD-10 code, based on the General Equivalence Mappings (GEMs). This ICD-10 to ICD-9 crosswalk tool is helpful for coders who need to reference legacy diagnosis codes for audits, historical claims, or approximate code comparisons.

Patient Education

Glaucoma

What is glaucoma?

Glaucoma is a group of diseases that can damage the optic nerve of one, or both, of your eyes. This can result in vision loss. There are different types of glaucoma, but the most common type is open-angle glaucoma. Other less common types include angle-closure glaucoma, and congenital glaucoma.

You may not have any symptoms of glaucoma. Regular eye exams by an eye care provider can check for glaucoma and other eye problems to help protect your vision. Treatments that lower eye pressure help slow the disease. Without treatment, glaucoma can eventually lead to blindness.

What causes glaucoma?

Medical experts aren't sure what causes glaucoma, but the most common types usually happen when the fluid pressure inside your eye slowly rises, damaging the optic nerve. Other types of glaucoma may be caused by medical conditions, or a baby may be born with it.

Not everyone with high eye pressure develops glaucoma. Some people may even get glaucoma with normal eye pressure. The amount of pressure your optic nerve can handle is different for each person. Getting regular dilated eye exams helps your provider figure out what level of eye pressure is normal for you.

What are the symptoms of glaucoma?

Often there are no symptoms of glaucoma at first. Or symptoms may start so slowly that you may not notice them. Without treatment, you slowly lose your peripheral (side) vision. It may seem like you're looking through a tunnel. Over time, your straight-ahead vision may decrease until no vision remains.

If you have sudden symptoms of intense eye pain, blurry vision, red eyes, or an upset stomach (nausea), you need to go to your eye care provider or an emergency room right away. These could be symptoms of angle-closure glaucoma. This less common type of glaucoma causes fluid to build up quickly in your eye.

How is glaucoma diagnosed?

A comprehensive eye exam can tell if you have glaucoma. This would include:

• A dilated eye exam. This involves getting eye drops that dilate (widen) your pupils. This allows more light to enter your eye. Your eye care provider examines your eyes using a special magnifying lens. This provides a clear view of important tissues at the back of your eye to check for glaucoma or other eye problems. For a few hours after the exam your vision may be blurry and sensitive to light, so you will need someone to take you home.
• Visual field testing. This check of your peripheral (side) vision allows your eye care provider to find out how well you can see objects off to the side of your vision without moving your eyes.
• Tonometry. This measures the pressure inside your eye.

If you're at higher risk for glaucoma, you should get comprehensive eye exams every one to two years. You're at higher risk if you:

• Are Black or African American and over age 40
• Are over age 60, especially if you're Hispanic or Latino
• Have a family history of glaucoma

You're also at higher risk if you have high blood pressure or diabetes and should get a dilated eye exam at least once a year. Talk with your provider about your risk and how often you should get your eyes checked.

What are the treatments for glaucoma?

Early treatment can help protect your eyes against vision loss. There is no cure, but glaucoma can usually be controlled. Without treatment it can eventually cause blindness. Treatments can include:

• Prescription eye drops are the most common treatment to lower the pressure in your eye and prevent damage to your optic nerve.
• Other treatments may include oral medicines, laser treatment, and/or surgery.

A combination of these treatments may be used to lower eye pressure and help drain the fluid out of your eye.

Can glaucoma be prevented?

There is no way to prevent glaucoma. Eye exams can help find glaucoma or other eye problems before they can affect your vision. If you have glaucoma, be sure to continue with treatment to prevent your vision from getting worse.

NIH: National Eye Institute

[Learn More in MedlinePlus]

Code History

• FY 2026 - No Change, effective from 10/1/2025 through 9/30/2026
• FY 2025 - No Change, effective from 10/1/2024 through 9/30/2025
• FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
• FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
• FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
• FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
• FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
• FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
• FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
• FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
• FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.