What Is Optical Coherence Tomography: A Comprehensive Guide 2024

During an eye exam, your eye doctor will likely perform a number of tests to assess your vision and the health of your eyes. 

They’ll check your eye pressure, examine the health of your retina and optic nerve, and more. And one of the ways they might do this is with a test called optical coherence tomography, or OCT.

So, what exactly is OCT? In this comprehensive guide, we’ll discuss everything you need to know about this eye exam, including what it is, how it’s performed, and what it can tell your eye doctor about your eye health.

What is Optical Coherence Tomography?

Optical coherence tomography or OCT is a non-invasive imaging technique that uses light waves to take cross-sectional images of your retina, the layer of tissue at the back of your eye that’s responsible for vision.

These high-resolution images provide your eye doctor with detailed information about the health of your retina and optic nerve. They also help your ophthalmologist to measure the thickness of your retina and optic nerve.

Healthcare providers also use optical coherence tomography to diagnose and monitor a number of eye diseases, such as age-related macular degeneration (AMD), glaucoma, and diabetic eye disease.

How is Optical Coherence Tomography Performed?

OCT eye test is a painless and quick test that takes about 15 minutes to complete.

To begin, your eye doctor will use dilating eye drops to widen your pupil. This can help the OCT machine get a clear view of your retina.

Next, you’ll sit in a chair and rest your chin on a chinrest attached to the OCT machine. The equipment then emits a low-level laser light into your eye without touching it. This light will reflect off different layers of your retina.

The pictures of these reflections are then displayed on a screen so your eye doctor can examine them.

Once the test is finished, your optometrist or ophthalmologist will go over the results with you. They’ll be able to tell you if there are any areas of concern on your eyes.

What Conditions Can OCT Help Diagnose?

OCT exams can be used to diagnose a number of different eye conditions, including:

Macular Hole

A macular hole is a small break in the macula, which is the part of the retina that provides sharp, central vision.

A macular hole can cause blurriness or a blind spot in your central vision. In some cases, macular holes can also cause distortion in your vision, where straight lines appear bent.

OCT scans can be used to diagnose macular holes by looking for changes in the structure of the macula. OCT can also help determine the severity of the macula hole and whether it is likely to cause vision problems.

Macular holes are usually treated with surgery, which involves making a small incision in the eye and using a laser to seal the hole. In some cases, they can heal on their own without treatment.

Macular Pucker

Macular pucker also known as epiretinal membrane is caused by the wrinkling of the retina. This can happen when the gel-like substance that fills the center of your eye (vitreous) shrinks and pulls away from the retina — a process called vitreous detachment.

As the vitreous detaches, it may tug on the retina, causing the retina to wrinkle. This can lead to changes in your vision.

You may see dark strings or specks floating in your field of vision (floaters). You also may see flashing lights or experience a temporary increase in the number of floaters. However, macular pucker does not usually affect your peripheral vision.

OCT can assist in detecting macular pucker because it reveals the retina’s wrinkling. If you have macular pucker, your doctor may recommend monitoring your condition or surgery to remove the membrane.

Macular Edema

Macular edema is one of the most common conditions that OCT can help diagnose.

Macular edema is a condition in which fluid accumulates in the macula, causing swelling and sensitivity. This build-up of fluid can cause blurred vision and even blindness if left untreated.

If your opthalmologist suspects you have macular edema, they will likely recommend an OCT scan to confirm the diagnosis. The scan helps to show the build-up of fluid in the macula, as well as any leakage or damage.

Age-Related Macular Degeneration

Age-related macular degeneration (or AMD) is a condition that affects older adults. It’s the leading cause of vision loss in people over age 50. It happens when the macula (the central part of the retina) begins to break down.

This condition is characterized by loss of central vision, which can make it hard to read or see fine details. However, people with AMD usually retain their peripheral vision, so they are not completely blind.

There are two types of AMD:

Dry AMD: This is the most common type of AMD. It happens when the cells in the macula dry out and get thinner with age. In dry AMD, OCT can show thinning of the macula and the presence of drusen.

Wet AMD: This is less common, but more serious. It happens when abnormal blood vessels grow under the retina and leak fluid or blood, scarring the macula. With wet AMD, vision loss can happen more quickly than with dry AMD.


Glaucoma is a condition that affects the optic nerve, and it can lead to vision loss.

OCT can help diagnose glaucoma by looking at the optic nerve head and assessing the amount of damage that has been done.

OCT can also help determine if there is any fluid buildup in the eye, which can be a sign of glaucoma.

If you have glaucoma, it is important to see an eye doctor regularly so that the condition can be monitored and treated if necessary.

Central Serous Retinopathy

Central serous chorioretinopathy is an eye condition that occurs when fluid accumulates under the retina.

The fluid leaks from the choroid (a layer of blood vessels that lies between the retina and the white of the eye).

This can cause the retina to detach from the back of the eye, leading to changes in vision, including blurry or distorted vision, as well as blind spots.

Central serous chorioretinopathy is thought to be caused by a breakdown in the barrier between the choroid and the retinal pigment epithelium (RPE). The RPE is a layer of cells that helps to pump fluid out of the choroid and into the space between the retina and the RPE.

When this barrier breaks down, fluid leaks out of the choroid and accumulates under the retina.

Though Central serous chorioretinopathy affects just one eye in most cases, it can occur in both eyes.

Diabetic Retinopathy

Diabetic retinopathy is a serious complication of diabetes. It occurs when high blood sugar levels damage the blood vessels in the retina, the light-sensitive tissue at the back of the eye.

When blood vessels in the retina are damaged, they can leak blood or fluid. This can cause the retina to swell and distort your vision.

Diabetic retinopathy often has no early symptoms, so it is important for people with diabetes to have regular eye exams. If left untreated, it can lead to vision loss and even blindness.

Vitreous Traction

The vitreous is a clear, gel-like substance that fills the inside of your eye. It helps to maintain the shape of your eye and gives it support.

In a young and healthy eye the vitreous is attached to the retina and the macula. As we age, the vitreous starts to shrink and pull away from the retina. This is a natural process and happens to everyone.

Sometimes, as the vitreous pulls away from the retina, it tug on it or cause it to become irritated. This can lead to a condition called vitreous traction.

Vitreous traction can cause the retina to become pulled or distorted. In some cases, it can even lead to a retinal tear or detachment, a condition known as posterior vitreous detachment (PVD). Sometimes, PVD can happen without any symptoms. But in other cases, it can cause flashing lights or floaters in your vision.

If you experience these symptoms, it’s important to see an eye doctor right away. They will be able to determine if you have vitreous traction and whether or not you are at risk for a retinal tear or detachment.

Who Can Participate? 

Individuals aged 25 and above or are at risk for ocular diseases, such as macular degeneration or glaucoma, may need to have regular OCT exams as part of their comprehensive eye exam. 

This is because ocular diseases often don’t have any symptoms in the early stages, when they’re most treatable. 

If you have risk factors for ocular disease, such as family history, diabetes, high blood pressure, or are African American, your doctor may recommend more frequent OCT exams.

Those with abnormalities or thickening of retinal layers may also be candidates for this test. Talk to your ophthalmologist about whether you should have this important eye exam.

 What Are the Risks?

There are a few risks associated with OCT. The first is that it uses light, and there is always a small risk of damage to the eye from too much exposure to light, especially for people with cataracts or heavy bleeding in the vitreous. 

OCT can also cause dryness and eye fatigue, so it’s important to take breaks and use artificial tears if needed. 

Finally, there is a small risk of retinal detachment with any type of imaging that uses light waves, but this is rare. 

Overall, OCT is a safe and effective way to get more information about the health of your eyes. It is painless and quick, and it can help your doctor to catch problems early. If you have any concerns about the risks, be sure to talk to your doctor.


Optical coherence tomography is an important tool that can be used to evaluate the health of your eye and detect a variety of eye diseases. This technology is non-invasive, painless, and provides high-resolution images. If your eye doctor suspects that you have an eye disease, they may recommend that you have an Optical Coherence Tomography exam. Talk to your eye doctor to learn more about this technology and how it can help you maintain healthy vision.


Frequently Asked Questions

What is the purpose of optical coherence tomography?

Optical coherence tomography is used to take high-resolution images of the retina, the innermost layer at the back of your eye. These images can help your doctor diagnose and monitor a variety of retinal diseases, including macular degeneration, diabetic retinopathy and glaucoma.

What is an optical coherence tomography scan?

An optical coherence tomography scan is a non-invasive test that uses light waves to take cross-sectional images of your retina. This test is often used to diagnose and monitor retinal diseases.

How does an optical coherence tomography work?

OCT is a type of imaging. It works similar to an ultrasound but uses light waves instead of sound waves. OCT creates a three-dimensional image of the eye. These images can help your doctor see problems with the retina, macula, and optic nerve.

What can an OCT scan detect?

An OCT scan can help your doctor detect a number of different eye conditions, such as, age-related macular degeneration, glaucoma, and diabetic retinopathy. Your doctor may also use an OCT scan to monitor the progression of these conditions.

What does OCT mean?

OCT is short for optical coherence tomography. It’s a type of imaging test that uses light waves to take pictures of your retina, the thin layer of tissue at the back of your eye.


Eric Gutenberg
Author: Eric Gutenberg

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