Optical Coherence Tomography

Optical coherence tomography, or OCT, is a non-invasive imaging technique that uses light to capture a picture of a tissue in the body. It is frequently used in ophthalmology, to look at the retina. Relatively long wavelength light enters the eye, and is scattered by the retinal tissue. Information about how the light is scattered within the retina is used to create a cross-sectional or three-dimensional image of the retina.

OCT has been an important tool for diagnosing MacTel and for tracking the progress of the disease. All participants enrolling in the MacTel Registry or who participated in the Natural History Observation Study have OCT scans done of their eyes. The resulting images are sent to the Moorfields Reading Center, where they are analyzed.

In addition to standard OCT, which is widely available in ophthalmology clinics, some of LMRI’s clinical sites and extramural collaborators have OCT angiography imaging systems. These are non-invasive imaging devices that have been specially developed for taking three-dimensional pictures of blood vessels in the retina.

OCT-angiography detects the motion of red blood cells through the vessels, looking at just a small area of the retina. OCT-angiography is well-suited for studying MacTel, where abnormal blood vessel growth is restricted to a relatively small area.

Extramural LMRI researchers are using OCT-angiography to study the blood vessel changes that occur with MacTel. Traditional fluorescein angiography allows clinicians to see pathological changes that develop in the blood vessels as a result of MacTel, but they provide only two-dimensional information. There are three layers of blood vessels in the human retina, and it is very hard to tell how individual layers of blood vessels are affected with traditional angiography. The three-dimensional images produced by OCT-angiography elucidate how different blood vessel layers in the retina are affected by MacTel.

Researchers affiliated with LMRI are studying new applications for OCT in studying MacTel. For example, OCT is being used to develop grading systems so that a standard metric can be used to describe disease progression. Also, OCT changes are being correlated with functional changes, as measured by microperimetry. OCT continues to be an important diagnostic and clinical research tool for Macular Telangiectasia type 2.