OCT

Optical coherence tomography (OCT) is a non-invasive imaging test. OCT uses light waves to take cross-section pictures of your retina. With OCT, your ophthalmologist can see each of the retina’s distinctive layers. This allows your ophthalmologist to map and measure their thickness. These measurements help with diagnosis. They also provide treatment guidance for glaucoma and diseases of the retina. These retinal diseases include age-related macular degeneration (AMD) and diabetic eye disease.

What happens during OCT?

To prepare you for an OCT exam, your ophthalmologist may or may not put dilating drops in your eyes. These drops widen the pupil and facilitate the examination of the retina.

You will sit in front of the OCT machine and support your head on a support to keep it still. The team will then scan your eye without touching it. The scan takes between 5 and 10 minutes.

Principles of Operation and Technology of Optical Coherence Tomography

Because the speed of light is extremely high, its echo time delay cannot be directly measured by electronics as in ultrasound. The echo time delays associated with light are extremely rapid. For example, the measurement of a structure with a resolution on the 10-micron scale, which is typical in OCT, corresponds to a time resolution of approximately 30 fsec (30 x 10-15 sec).

Direct electronic detection is not possible on this time scale. Instead, it is necessary to use correlation or interferometry techniques. One method for measuring the echo time delay of light is to use low-coherence interferometry. Low-coherence interferometry was first developed for measuring reflections in fiber optics and optoelectronic devices [48–50]. The first applications of low-coherence interferometry in biomedicine were in ophthalmology to perform precision measurements of axial eye length and corneal thickness

What is an OCT test used for?

OCT is an imaging method used to create an image of the back of the eye, called the retina. The image is created by accurately measuring the amount of faint red light that is reflected off the retina. OCT is commonly used to image the eyes of glaucoma patients.