Glaucoma
What does an OCT scan show in glaucoma?
OCT, or optical coherence tomography, takes a cross sectional scan of the retina and optic nerve using light, with no contact and no radiation. In glaucoma it measures the thickness of the nerve fibre layer around the optic disc in microns and compares it with normal values and with your earlier scans, often detecting damage before the visual field changes.
What the scan involves
You rest your chin on a support and look at a target while the machine scans for a few seconds per eye. Nothing touches the eye and there is no injection. Many modern scans are taken without dilating drops, although drops may be needed if the pupil is small or the media are hazy.
What your ophthalmologist reads
- Retinal nerve fibre layer thickness around the optic disc, shown as numbers and a colour coded map
- Neuroretinal rim measurements at the disc itself
- Macular thickness, where the ganglion cell layer is also affected in glaucoma
- Progression analysis, comparing today's measurements with all previous scans
- Scan quality, since poor signal can mimic thinning
Strengths and limits
OCT is objective, repeatable and sensitive to early structural loss, which makes it valuable in glaucoma suspects. It does not measure how well you see, so it complements rather than replaces the visual field test. In very advanced glaucoma the nerve fibre layer reaches a floor and fields become the better measure of change.
At Standard Eye
OCT imaging is carried out in house at our hospital in Garki, Abuja, and used both at diagnosis and for long term monitoring of glaucoma and retinal disease.
Frequently asked questions
- Is OCT safe and does it hurt?
- Yes it is safe and no, it does not hurt. It uses light rather than X-rays and nothing touches the eye.
- How often will I need one?
- Commonly once or twice a year in treated glaucoma, more often when the diagnosis is uncertain or the condition appears to be progressing.
Concerned about these symptoms?
Arrange an eye examination with our consultant ophthalmologist in Garki, Abuja.
Care at Standard Eye
Related answers
- Which tests are used to diagnose glaucoma?
- What is a visual field test like?
- What are the early signs of glaucoma?
- What is eye pressure, and what is a normal reading?
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