The purpose of the duochrome test during your eye exam

The duochrome test is a helpful tool used by eye care professionals to check how well your eyes focus. As the name of the test suggests, it involves two colors—red and green—and in certain cases, it can help eye care professionals find the right prescription for your vision.

Duochrome test basics

Different colors of light focus at different distances when they go through your eyes. Red light has a longer wavelength than green light, and your eye care professional can use this unique property of light when testing your eyesight. During the duochrome test, they’ll show you letters against a split red and green background and you’ll be asked which side the letters are clearer on. Your eye care professional will fine-tune your prescription, adjusting with more or less magnification depending on your answers.

What to expect at a duochrome test

First, determining if a duochrome test is necessary

A woman sits in an exam chair in an eye doctor's office talking to a female eye doctor

Your eye care professional will decide if you’d benefit from a duochrome test during your comprehensive eye exam. To do this, they’ll check your overall eye health and test your vision with a variety of tests. During these tests, it’s important to communicate any concerns or vision issues you have. The feedback you give them helps them determine if you need any additional testing like the duochrome test.

When is a duochrome test used?

Duochrome tests are not used as commonly as other vision tests that you may be familiar with, like the eye chart or the phoropter. It depends on the needs of your eyes. For certain people, the duochrome test may help refine your prescription so that you aren’t over- or under-corrected. This can help with overall eye comfort because the more precise your prescription, the better the chance you’ll experience less eye strain and discomfort in your day-to-day life. That said, the duochrome test doesn’t work for everyone, so it’s up to your eye doctor to determine if it’s useful. For instance, if your vision is worse than what’s known as 20/40, the test might not give reliable results, since the differences between red and green may be too small to notice.

First, determining if a duochrome test is necessary

A woman sits in an exam chair in an eye doctor's office talking to a female eye doctor

Your eye care professional will decide if you’d benefit from a duochrome test during your comprehensive eye exam. To do this, they’ll check your overall eye health and test your vision with a variety of tests. During these tests, it’s important to communicate any concerns or vision issues you have. The feedback you give them helps them determine if you need any additional testing like the duochrome test.

Setting up the duochrome test

Duochrome chart

This is a special chart that shows letters on a chart that’s half red and half green. It helps in assessing how well you can see with each color.

Lens holder

A device called a phoropter or trial frame holds the lenses in front of your eyes during the test so your doctor can easily switch them out.

Dim light

The test is typically conducted in a dimly lit room so your pupils can fully open up, improving the accuracy of the test.

Duochrome, step by step

Positioning for the test

You’ll sit some distance away from the duochrome chart, usually around 20 feet. This can also be set up in a smaller room with a mirror to simulate the distance.

Performing the test

Your doctor will cover one eye so you can focus on the chart. You’ll then compare how the letters look against a split red and green background.

Adjusting lenses

If one color seems clearer than the other, your eye care professional will adjust the lenses until both colors look as equal as possible.

Final adjustments

Once everything looks as balanced as possible, you might receive your final prescription, or your doctor may suggest further testing if needed.

Don’t miss your annual eye exam

The duochrome test can be an important part of checking your vision. It can help make sure your glasses or contacts provide you with the best possible prescription. Even so, a duochrome test is not right for everyone, so talk to your eye care professional about what eye tests are right for you. If haven’t scheduled your annual exam yet, it can be a great time to get that scheduled as well. Your eye health is an important part of your overall health!

FAQs

Frequently asked questions

What is the purpose of a duochrome test?
The duochrome test is used to help eye care professionals find the right lens prescription for you. It shows how clearly you can see when looking at red and green colors, which can tell the doctor more about your vision.
What is the alternative to the duochrome test?
An alternative to the duochrome test is using different types of lenses or visual acuity tests that measure how well you can see letters or shapes. These methods also help eye doctors determine if you need glasses or other vision corrections.
Why do eye care professionals ask if red or green is clearer?
Eye care professionals ask if red or green looks clearer to help choose the best lenses for your eyes. Your answer helps them figure out how your eyes focus light and what kind of vision correction you might need.

Related content

An eye doctor gives a patient an eye exam using a phoropter

How to get contact lenses

A woman looks into a mirror and smiles

Prepare for an appointment

The information provided on this page and across the entire Acuvue.com experience is designed to offer educational insights into eye health, referencing expert advice from reputable medical and government organizations, including the American Academy of Ophthalmology, the American Optometric Association and the National Eye Institute. While we research, report, and review the content on Acuvue.com and its extended social media to deliver accurate and up-to-date vision, vision care, and vision correction information, we do not make any assurances, and content accessed on or through Acuvue.com and its extended social media is not intended to replace professional medical advice, diagnosis, or treatment of any eye conditions or health issues. This brings us to our #1 eye health tip: Always consult a qualified healthcare professional for personalized medical guidance and care.

2025PP07296
ACUVUE navy logo in capital letters
We support the AdvaMed Code of Ethics on interacting with Healthcare Professionals.
Advamed Logo
Get Contacts
Help & Customer Care
MyACUVUE®
About
Legal
© Johnson & Johnson and its affiliates 2025. All rights reserved. This site is published by Johnson & Johnson Vision Care, Inc., which is solely responsible for its content. It is intended for use by residents of the United States.

Third-party trademarks used herein are trademarks of their respective owners.