Optical Coherence Tomography

Optical coherence tomography (OCT) is a noninvasive imaging method that uses reflected light to create pictures of the back of your eye. It can be used to diagnose and manage diseases like diabetes-related retinopathy and glaucoma.


What is optical coherence tomography?

Optical coherence tomography, or OCT, is an imaging method used to generate a picture of the back of your eye, called your retina. The noninvasive method produces an image by measuring the amount of a dim red light that reflects off of your retina and optic nerve. Optical coherence tomography can measure the thickness of your retina and optic nerve.

Healthcare providers of heart and vascular medicine use optical coherence tomography for cardiac catheterization to produce images of your blood vessels. Healthcare providers in the dentistry, gastroenterology, pulmonology, dermatology and oncology fields are also using OCT imaging more often.


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What is optical coherence tomography angiography?

Traditional angiography, also called arteriography, refers to examining the inside of blood vessels using X-rays. Typically, your healthcare provider injects a radiopaque dye that shows up on the X-rays. Eye care professionals also use a special type of angiography to examine blood vessels of your retina. The dye used glows when exposed to a blue light.

Eye care professionals can also use optical coherence tomography angiography to see inside the blood vessels in your eye. Unlike traditional angiography, the test is completely noninvasive and a dye doesn’t need to be injected.

When is optical coherence tomography performed?

Your eye care professional suggests optical coherence tomography if they suspect you have certain conditions at your eye exam or if you already have a condition that they’re helping you manage.

Healthcare providers use OCT to diagnose and manage several conditions that affect the eyes, including:

  • Glaucoma: If you have glaucoma, fluid and pressure build up in your eye and damage your optic nerve.
  • Age-related macular degeneration: People may lose central vision with this condition. It’s a progressive disease related to aging but, fortunately, treatments are available for some forms.
  • Diabetes-related retinopathy: Diabetes damages the small blood vessels of your eye leading to vision loss. Fluid can leak out of your eye causing blurry vision. In severe forms, your entire retina can detach from the back of your eye and glaucoma may develop. People can become completely blind, but with treatment, diabetes-related retinopathy can be controlled.
  • Cystoid macular edema: Macular edema refers to the swelling of your macula with fluid. Your macula is the part of your retina that has the most light-sensing cells.
  • Macular pucker: Scar tissue can grow over the surface of your retina causing distorted vision. Surgery can sometimes help.
  • Macular hole: A macular hole happens when your retina pulls apart forming a hole in your macula. This can affect your vision, but can be repaired by surgery.
  • Cone and cone-rod dystrophies: These conditions affect the cells of your eyes that are sensitive to light and color. When the condition worsens, you can have vision loss.
  • Tumors in your choroid and retina: These cancers happen in your retina and your choroid, a vascular layer found between your retina and your sclera.


When would optical coherence tomography be needed?

Your optometrist or ophthalmologist may recommend that you have an optical coherence tomography procedure if you’re over a certain age and/or at risk of developing certain eye diseases. Some healthcare providers may suggest OCT scans be included regularly in your schedule of eye exams so they can monitor the thickness of the layers in your retinas.

Your healthcare provider will likely recommend optical coherence tomography if you’re having treatment for certain eye conditions. Both optometrists and ophthalmologists perform the procedure.

Test Details

How does optical coherence tomography work?

Optical coherence tomography uses a low-powered laser to create pictures of the layers of your retina and optic nerve. The cross-sectional images are three-dimensional and color-coded.


What should I expect if I’m having an optical coherence tomography exam?

There’s no special preparation needed for an OCT test.

You’ll sit down and rest your chin on a support attached to the machine. The OCT equipment will scan one eye at a time. You’ll focus your eyes on a green target within the machine. You may see a red line while you’re having the scan. The test will take minutes.

Nothing touches your eye.

What are the risks of optical coherence tomography?

There aren’t any risks or side effects associated with optical coherence tomography scans, except possibly some dryness or eye fatigue. However, because this type of test relies on light, OCT isn’t effective if you have thick cataracts or heavy bleeding in your vitreous. Your vitreous is the gel that fills your eyeball.

Results and Follow-Up

What type of results do you get and what do the results mean?

Your healthcare provider will evaluate the images from the optical coherence tomography test and go over them with you. They may need time to compare older scans to the newest ones. You should have the results quickly.

When should I call my healthcare professional?

It’s important to get regular examinations. In between, call your healthcare professional if you have:

  • Eye pain.
  • Trouble seeing clearly.
  • Trouble seeing colors.

A note from Cleveland Clinic

If your healthcare provider suspects you have certain types of eye disease, or if you’re at risk for certain diseases, they might suggest that you have an optical coherence tomography test (OCT). This noninvasive test doesn’t hurt. It’s very important to diagnose any type of eye disease early, and OCT helps do that. Talk to your doctor if you start experiencing changes in your eyes.

Medically Reviewed

Last reviewed on 04/25/2022.

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