Optical coherence tomography

Optical coherence tomography (OCT) is a laser imaging method used to produce a detailed cross-sectional map of your retina, the cells at the back of your eye that translate light into images. This non-invasive technique creates images by measuring the reflection of a dim red light off your retina and optic nerve (which sends messages from your eye to your brain).

The OCT at The London Clinic can also assess blood vessels, known as OCT angiography. These images allow your ophthalmologist to view and assess your retina, measure the thickness of each layer, and examine the macula at its centre. OCT can also help detect glaucoma by identifying changes in the optic nerve.

What is optical coherence tomography used to test?

The major application of optical coherence tomography (OCT scan) is for diagnosing and monitoring retinal disease and glaucoma. However, it can also be used to monitor the progression of conditions that affect other areas within your eye.

OCT scans are most commonly used to diagnose and manage conditions, such as:

• Diabetic eye disease – A group of eye conditions (including diabetic retinopathy and macular oedema) caused by prolonged high blood sugar levels, which can lead to damage to the blood vessels in your retina. OCT can assess whether the damage caused to the blood vessels in your retina has resulted in diabetic macular oedema (swelling of the macula). OCT angiography can assess if the blood vessels in the retina and macula have been damaged by diabetes.
• Retinal vein occlusion – The blockage of a retinal vein, which prevents blood from leaving your retina, resulting in increased pressure inside your eye and swelling. OCT can assess whether a blocked retinal vein has led to macular oedema, and OCT angiography can assess the integrity of the remaining blood supply.
• Age-related macular degeneration (AMD) – A disease that occurs when the macula begins to show signs of ageing. It can be caused by a build-up of deposits on the macula (dry AMD) or leaking blood vessels underneath or within the macula (wet AMD). Most commonly, OCT is used to diagnose and monitor wet AMD, in which abnormal blood vessels leak and damage the retina. OCT angiography can show the abnormal new blood vessels.
• Glaucoma – A condition that occurs when your eye’s drainage channels become blocked, leading to a build-up of pressure within the eye that can damage your optic nerve. OCT is used to assess whether this increased pressure has resulted in any damage to the optic nerve.
• Central serous chorioretinopathy – An eye condition that occurs when fluid builds up under the retina, causing a localised detachment of the retina. OCT can be used to detect and monitor central serous chorioretinopathy.
• Macular hole – A condition in which a hole develops in your macula when the vitreous (the clear gel that fills the eye) shrinks with age and pulls away from the macula. OCT can provide a clear image of the macula so that your consultant can confirm a diagnosis of macular hole.
• Uveitis – An inflammation of the eye that can lead to fluid in the macula. OCT can help your consultant to view the inside of your eye clearly, allowing them to assess any macular fluid. OCT angiography can assess the effect of uveitis on the blood vessels.

Are there any risks associated with optical coherence tomography (OCT)?

OCT is generally considered a risk-free procedure, though you may experience some dryness or eye fatigue temporarily following the scan.