Learning About Optical Coherence Tomography

Optical coherence tomography, or OCT, is an eye imaging test that uses light waves to create detailed pictures of the back of your eye. Your doctor can use these pictures to look closely at the retina and the optic nerve.

The OCT machine never touches your eye, and there is no radiation involved.

Because the images are three-dimensional, your doctor can see the different layers of the retina, not just the surface. A newer version called OCT angiography (OCTA) can also show the tiny blood vessels in your eye, without the dye that's used in typical angiography.

OCT gives eye doctors a level of detail that is hard to get any other way. It can pick up changes in the retina that might not cause symptoms yet. This is one reason it has become such a common tool in eye care.

Doctors use it to diagnose and keep track of a number of eye conditions, including:

• Age-related macular degeneration (AMD).
• Glaucoma.
• Diabetic retinopathy.
• Macular edema.
• Retinal detachment.
• Macular hole.

Your doctor might recommend OCT if you are over 40 or if eye disease runs in your family. OCT is also useful for tracking whether a treatment is working. Because it measures the thickness of retinal layers, your doctor can compare scans over time and spot even small changes.

The exam does not hurt. In some cases, your doctor will use eye drops to widen (dilate) your pupil before the scan. This gives the machine a better view.

During the scan, you rest your chin on a small support to keep your head steady and look at a fixed point inside the machine. You might notice a faint red line moving across your field of view. That is the scanner at work. The whole exam takes about 5 to 10 minutes, and the machine never makes contact with your eye.

If your eyes were dilated, they may be sensitive to light for a few hours and your vision might be slightly blurry, but both effects wear off on their own. Your doctor will go over the results with you and explain what the images show.