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What is an OCT eye test – and what does it do?

What is an OCT eye test?

Cascadia Eye

OCT eye examCascadia Eye

Conducting an OCT eye test

Cascadia Eye has an OCT device at five of our locations. But unless you have glaucoma (or a family history of it), macular degeneration, or diabetic retinopathy, you may never have seen this amazing piece of technology at work. And if you have received an OCT test before, now you can find out what it actually does, and how!

What is the OCT?

Conducting an OCT eye testIt’s not just the abbreviation for October – in ophthalmology, OCT stands for Optical Coherence Tomography. At its most basic description, the OCT “takes pictures of the back of your eye.” From a patient standpoint, this simply means you sit at the machine and place your head as directed, and shortly thereafter the technician tells you they have the images they need and you go on to the next portion of your eye exam. But it’s so much more than that.

“The OCT is an excellent way to visualize the different layers of the retina and optic nerve in a living eye. Previous to these amazing technologies we were only able to see this view of an eye with tissue sections after the patient was deceased or if the eye was removed. The OCT allows us to diagnose and manage various eye problems like glaucoma and macular degeneration with greater accuracy and sensitivity.” – Dr. Dan Siapco

The best description I’ve heard for how the OCT functions is that it’s like an ultrasound, except it uses laser light* – instead of sound waves – to map the shape of the retina and optic nerve. It’s non-invasive and not destructive to tissue; a camera-like device directs the waves of light, which bounce back with an accurate 3-D picture.

Here’s a sample of what the technicans and doctors see once the images are taken:Measurement centering with Foveafinder


The OCT and your eye health

So what do these colorful pictures mean? A doctor looking at the above image knows what a healthy retina and optic nerve will look like – how thick and/or even it should be, and more. Because the OCT’s map of the eye is in 3-D, doctors can detect areas of the eye that are abnormal or damaged early on (for example, if they have a blister of fluid in a layer of the retina), before it has affected the vision of the patient. Early detection means we can treat diseases like glaucoma, or halt the progress of macular degeneration, before they cause irreversible vision damage.

For a (somewhat amusingly) dated – but informative – look at the OCT when it first came out, you can also watch this video. The technology has gotten even better since then; it is also much more widespread in its use, which is a wonderful thing!

Contact Cascadia Eye

If you would like to learn more about the OCT, or if you would like to schedule an appointment at Cascadia Eye, please contact us today. We are happy to answer any questions you might have!

In addition, join us on Facebook, Twitter, or Google+ to ask your questions about eyes, exams, and our practice. We’d love to hear from you – and there might be a blog to address your questions in the future.


*The light is actually a ‘laser-like’ light source known as a super luminescent diode (SLD).

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