What is OCT?

It stands for optical coherence tomography and is based on the imaging of reflected light. Unlike a camera, it can resolve depth, at a very fine level. The resolution can be down to 0.01mm and provides us with a very nice cross-sectional view of the retina.

How does it work?

A beam of infrared light is scanned across the retina. The machine collects the reflected light and measures its “time of flight” delay. That is, light coming from deeper layers takes longer to return compared to light from superficial layers. The light does not interfere with or affect the retina. The various reflections are then built up into an image with computer generated colours. It is not a photography nor an x-ray.

What does it tell us?

OCT reveals structural or anatomical changes in the retina. It does not assess the function of the retina although conclusions can be made based on the OCT. There are many conditions that cause anatomical changes in the retina, particularly macular degeneration, but also macular holes and macular fibrosis. OCT is very useful in monitoring treatment of macular degeneration in those patients having injections of Lucentis or Avastin. OCT also can assess the health of the nerves of the eye and this is useful in managing patients with glaucoma. Scans can be done to look specifically at the nerve fibres in the retina and also at the structure of the optic nerve. The optic nerve is the cable that links the eye to the brain.

How is OCT done?

This part is really easy. All the patient has to do is look at a yellow-green spot inside the machine and technology does the rest.

Here are some sample images. Please click on the thumbnail to view enlargement.

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