Optical Coherence Tomography (OCT)

Optical Coherence Tomography (OCT)

Optical Coherence Tomography (OCT) is a promising new class of diagnostic medical imaging technology that combines the principles of ultrasound with the imaging performance of a microscope. This enables the ophthalmologist to look at the eye in microscopic detail in a clinical setting. Whereas ultrasound produces images from backscattered sound "echoes," OCT uses infrared light waves that reflect off the internal microstructure within the biological tissues. This results in greatly increased image resolution - 8-25 times greater than any other existing modality.

While standard electronic techniques are adequate for processing ultrasonic echoes that travel at the speed of sound, interferometric techniques are required to extract the reflected optical signals from the infrared light used in OCT. The output, measured by an interferometer, is computer processed to produce high-resolution, real time, cross sectional or 3-dimensional images of the tissue. This powerful technology provides in situ images of tissues at near histological resolution without the need for excision or processing of the specimen.

As a result of this high level of resolution, OCT is particularly suitable for retinal thickness measurements. OCT images can be presented as either cross sectional images or as topographic maps. Cross-sectional images take advantage of the well defined boundaries in optical reflectivity at both the inner and outer margins of the neurosensory retina allowing for retinal thickness measurement. Retinal thickness can then be assessed longitudinally using serial OCT images.