The Optical Coherence Tomography (OCT) scan

Published 07 May 2024

Optical Coherence Tomography (OCT) scans are available across all GMHBA Eye Care locations and may be part of your next eye examination. Find out more about this important piece of equipment and what you can expect below.


What is an Optical Coherence Tomography (OCT) scan?

This non-invasive piece of diagnostic equipment captures a series of advanced 3D scans of the back of the eye. An OCT scan can assist with the diagnosis and management of eye conditions including glaucoma, macular degeneration and diabetic retinopathy.   


How does an OCT work?  

The OCT scan has some similarities with an ultrasound in that it provides real-time images of the back of the eye. An OCT scan uses harmless light waves, instead of sound waves, to illuminate and scan your retina, the light-sensitive part of the eye. This allows your optometrist to examine your retina in an extremely detailed way.  

OCT scan image

Above: Detailed imagery of the eye from an Optical Coherence Tomography scan.


What happens during an OCT scan?  

An OCT can be done with or without dilating eye drops. Dilating drops may be used to widen the pupil and help capture detailed images. Most patients find dilating drops to be painless however some light sensitivity and blurred vision can be expected for a few hours afterwards.

Like other tests you may do during your eye examination, you will place your forehead and chin on a rest in front of the machine. Your optometrist will then guide you through the scans and a fixation light is used to ensure you are looking in the correct direction for each scan. The scans will take about 5-10 minutes to do. 


What does an OCT measure?  

The retinal tissue has 10 layers, and the OCT scans allow each layer to be captured with detail. An OCT can capture detail of 8-10um resolution, which is similar to the thickness of a strand of hair! This allows even the slightest, and earliest change to be identified.  


Do I need an OCT?  

This is a great discussion to have with your optometrist. They may recommend that patients at higher risk of certain eye conditions have an OCT scan more often to monitor and watch for any changes.

Even for those who don’t have an increased risk of eye disease, a baseline OCT is an excellent reference for your optometrist to have, allowing them to detect and manage even the smallest of changes in your eyes.  

All of our optometrists are on hand to help if you have any questions regarding this piece of equipment.


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