OCT is an imaging scan that uses light waves to take detailed images of the eye. Doctors can use it to diagnose many eye conditions, including macular degeneration.
Optical coherence tomography (OCT) provides cross-sectional images of the retina, the light-sensitive layer at the back of the eye that communicates with the brain and enables people to see.
The macula is the part of the retina that allows central vision so people can see objects or text directly in front of them. Damage to the macula can lead to age-related macular degeneration (AMD), an eye disease causing loss of central vision.
Doctors may use OCT to help them diagnose AMD and monitor treatment progress.
This article looks at how OCT works and how both types of AMD show up on OCT scans. It also outlines the procedure and offers advice on how to live with AMD.
OCT is an imaging scan that doctors use to diagnose certain eye diseases. During an OCT test, light waves take cross-sectional images of the retina.
This allows a doctor to see the retina layers and measure their thickness, which can help with diagnosis.
OCT is a quick, safe, and noninvasive imaging test, and
Learn about other tests for AMD here.
Doctors may use OCT to diagnose AMD. OCT can provide highly detailed images of the retina and macula, which is the part of the retina affected by AMD.
Learn more about AMD here.
OCT can help to diagnose various eye conditions, including:
- macular hole, which is a tear in the macula
- swelling of the macula
- macular pucker, a bulge or wrinkle in the macula
- glaucoma, an increase in intraocular pressure in the eye that damages the optic nerve
- diabetic retinopathy, when diabetes damages blood vessels in the eye
- central serous retinopathy, a buildup of fluid underneath the retina
- vitreous traction, when the vitreous, a gel-like substance in the eye, separates from the retina and pulls on the macula
OCT can also examine the fibers of the optic nerve, so it is useful for diagnosing conditions involving the optic nerve.
As OCT uses light waves, it cannot diagnose conditions that affect how light travels through the eye, such as dense cataracts or vitreous bleeding.
Learn more about the eyes and how they work here.
An OCT scan
OCT also examines the choroid, a layer of tissue between the sclera — the white outer layer — and the retina at the back of the eye. The choroid contains blood vessels that supply the eye with nutrients and oxygen.
Images from OCT can show:
- drusen, small deposits of protein and lipids that collect under the retina
- the structure of the retina
- any new or abnormal blood vessels
- any bleeding within the eye
How wet and dry AMD show up on OCT scans
There are two types of AMD. OCT can identify signs of each type.
- Dry AMD: This is the most common type of AMD. It occurs when parts of the macula become thinner and drusen in form, causing a slow loss of vision.
- Wet AMD: New, abnormal blood vessels growing under the retina can indicate wet AMD. The blood vessels can leak blood or fluid, which scars the macula and can cause vision loss to occur more quickly than dry AMD.
AMD affects central vision, and people with the condition may have difficulty seeing fine details directly in front of them. People’s peripheral vision may remain the same.
Learn about the difference between wet and dry AMD here.
Before a person has an OCT scan, an eye doctor may put drops into their eyes to dilate the pupils. This allows a clearer examination of the retina.
During the exam, a person will sit upright on a chair in front of the OCT machine and rest their chin on a chinrest to keep still. The eye doctor will align the machine with the eye they are testing and scan the eye.
OCT is noninvasive and does not involve touching the eye. A person will need to keep their head still while the machine is scanning, which may take 5–10 minutes.
After the exam, a person will be able to resume their normal activities. If a person had dilating eye drops, their eyes might be sensitive to light for several hours following the OCT.
An eye doctor will usually share the results of the OCT with a person right away.
People with AMD may work with a vision rehabilitation team. The team can help them make adjustments to cope with vision loss and learn to use low vision aids.
Low vision aids may help people carry out everyday tasks more easily and help prevent falls. Low vision aids may include:
- magnifying tools, either as glasses or handheld devices
- glasses that help increase contrast or reduce glare
- camera and computer devices that magnify objects, such as a piece of text from a book, onto a screen
- telescopic devices that can attach to glasses, or binoculars
- large-print books or audiobooks
- computer software that reads out text
People may also have to rely more on their other senses, such as:
- listening for sounds that will indicate a certain area or object, such as traffic sounds that indicate an open window
- listening to books and audio devices instead of reading
- choosing items of clothing based on the feel and texture of fabrics
- using a cane or walking aid to feel even surfaces or objects when walking
- learning to increase the use of peripheral vision
People can also talk with their healthcare team about nutrition and supplements to help slow the progression of dry AMD, such as:
- vitamin C
- vitamin E
Learn more about supplements for AMD.
Early diagnosis and treatment of AMD is important, as early-stage or dry AMD
OCT is an imaging test that produces detailed images of the retina. OCT helps doctors diagnose eye conditions, including AMD.
OCT is a quick, noninvasive test. People will sit in front of the OCT machine while a laser light scans the eye.
People may have dilating eye drops to widen the pupil, making the eyes temporarily more sensitive to light following the test.
Early diagnosis and treatment of AMD can help prevent the disease from progressing. OCT can also help doctors monitor treatment progress.