As technology advances, optical health specialists have an increasing array of advanced tests and diagnostics they can use to pinpoint problems in your eye. The optical coherence tomography (OCT) test is one of the newest developments in optometry, but you may not immediately appreciate what the test entails or why your optometrist has recommended this procedure for you. Learn what to expect from an OCT test here, and find out why this technology is so beneficial.

How an OCT test works

Optical health problems are often difficult to diagnose. This part of your body is particularly delicate, and it's also often tricky for an optical health specialist to see the sections of your eye that are causing problems. For example, a number of conditions affect the optical nerve, but the placement of the nerve behind the eye means that diagnostic examinations are complex.

OCT technology offers ophthalmologists a state-of-the-art technique that can help diagnose many serious conditions. Crucially, an OCT test is non-invasive, which means it's easy for a specialist to administer the procedure without preparation or side-effects for the patient.

An OCT scanner uses 3-D imaging technology to create a detailed, complex picture of your eye. The test is rather like the ultrasound scan that a doctor or nurse can use to examine an unborn baby without harming the mother or her child. Most importantly, an OCT scan builds up a comprehensive image of your eye's internal structure in a way that just isn't possible from other tests and diagnostics.

At the back of your eye, you have a layer made of light-sensitive cells called the retina. When light hits these cells, the retina triggers nerve impulses that pass along the optic nerve to your brain. An OCT test scanner uses light waves to take multiple cross-section pictures of the retina.

What your ophthalmologist looks for

The ophthalmologist will closely examine the images to look for signs of damage, illness and disease. The OCT images allow the ophthalmologist to map and measure the retina's thickness. If the retina has increased or decreased in thickness, a specialist can often diagnose the cause of any problems, particularly when he or she uses the digital images with a traditional physical examination.

OCT allows ophthalmologists to spot the early signs of several serious optical conditions. Early diagnosis can often make it easier to treat these problems and/or prevent them getting worse. Conditions that an OCT test can diagnose include:

• Glaucoma – a disease of the optic nerve that can eventually lead to blindness
• Macular degeneration – a problem that affects the center of your retina and may lead to vision loss
• Diabetic maculopathy – where damage to the blood vessels in the retina can eventually lead to blindness
• Macular holes – tiny holes in the retina that can lead to vision deterioration

The symptoms of these conditions are often similar, so, without an OCT test, your ophthalmologist may find it hard to prescribe the right sort of treatment.

That aside, you can't use an OCT test to diagnose any condition that stops light passing through the eye. For example, dense cataracts block the passage of light to your retina and will interfere with an OCT test.

What happens during the test

An OCT test is a short, painless procedure. Before the test, your ophthalmologist will normally use eye drops to dilate your pupils. These drops make the pupil larger, which makes it easier for an eye doctor to examine the inside of the eye.

Once the pupils dilate, your eye doctor will ask you to sit in front of the machine and rest your head on a special support. It's important to keep your head still during the test, so your doctor can get high-quality images. The OCT scanner will then scan your eye for up to 15 minutes. The scanner won't touch your eye, but you may feel some light-sensitivity for a few hours because of your dilated pupils.

OCT tests are increasingly common for patients where a specialist believes there is a retinal problem. These simple, painless tests can aid early diagnosis and help thousands of people manage the symptoms of optical health issues. Click here to read more about tests your eye doctor may use to help them diagnose and treat any problems with your eyes. 

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