Optical Coherence Tomography
OCT Scans at Aves Optometrists
Until fairly recently, we have been able to examine your eyes using a variety of instruments, all of which show us what is going on at the surface of the retina. This has enabled us to detect and diagnose a wide variety of eye conditions such as glaucoma, age related macular degeneration and diabetic retinopathy, to name but a few. OCT is an amazing new piece of technology which allows us to go one step further. In a few seconds, the OCT safely and painlessly scans the back of the eye, providing a 3D view through and beneath the retina. The information provided by OCT scans enables us to detect and diagnose a wide variety of eye conditions at the very earliest stage.
OCT and Glaucoma
Glaucoma is a common eye condition, which for many years has been associated with high pressure in the eye. But detecting glaucoma is much more complicated than simply measuring eye pressure and modern definitions of glaucoma do not even mention eye pressure.
Glaucoma is an eye disease that causes a progressive loss of nerve fibres from the optic nerve and retina, resulting in a gradual loss of vision. This process is usually slow and painless and the loss of vision often does not become apparent to the individual until very advanced (when up to 90% of the nerve fibres have already been lost). Such damage to the optic nerve cannot be repaired and so it is imperative to detect glaucoma at the earliest possible stage so that suitable treatment can be initiated to prevent further visual loss.
The OCT allows us for the first time to actually measure, with incredible accuracy, the thickness of the nerve fibre layer in the retina and optic nerve head. The instrument can then compare this result for any individual with the result for a ‘normal’ optic nerve to indicate whether nerve fibres have been lost and therefore whether glaucoma may be present. By repeating his measurement at subsequent eye examinations it is possible to detect subtle changes to the nerve fibre layer which may indicate the very earliest sign of glaucoma. Current estimates suggest that OCT detects early stage glaucoma 3 years earlier than conventional pressure measurements and/or visual fields assessments.
OCT and Diabetic Retinopathy
In diabetic retinopathy, the growth of abnormal new blood vessels leads to leakage from these vessels and subsequent damage to the retina. The OCT is able to detect leakage within the retina and below the retina as well as leakage visible on the surface of the retina. This means that diabetic retinopathy can be seen, even when it’s not visible using digital retinal photography.
OCT and Age Related Macular Degeneration (AMD)
Many people have heard of the eye condition AMD which causes blurring and/or distortion of the central part of vision, affecting an individual’s ability to see detail such as print or people’s faces. AMD can lead to complete loss of central vision and it is now the leading cause of blindness in the UK.
There are two types of AMD: wet and dry. Dry AMD is much more common than wet and thankfully it affects vision less. There is currently no effective treatment for dry AMD but there are ways of halting or slowing down the progression of it – see our patient information section on AMD.
Many people may have signs of dry AMD for many years without any serious effect on their vision.
A minority of people develop wet AMD. This involves the development of abnormal new blood vessels underneath the macula (the central part of the retina) which then (as the name implies) leak fluid into the retina. Over a very short period of time this can cause distortion and severe loss of central vision. In recent years great strides have been made in developing effective treatments for wet AMD.
Whenever we examine your eyes, we are always looking for signs of AMD and particularly any signs that could indicate the presence of wet AMD. The OCT allows us to see the area where new blood vessels or fluid leakage may occur. By detecting these signs at a very early stage, treatment can be initiated quickly to stabilise the condition and prevent loss of vision.
So who should have an OCT Scan?
We recommend that anyone with specific concerns about glaucoma, AMD or diabetic retinopathy has an OCT scan at each visit for an eye examination. We will advise you whether that should be every year or every two years depending on your individual risk factors or concerns.
An OCT is also useful for early detection of ocular signs in many systemic health conditions, such as multiple sclerosis, raised blood pressure and cancer.
To get a complete picture of the health of your eyes, we recommend an OCT scan for all adults, particularly anyone over 40 years old, as increasing age is a significant risk factor for both glaucoma and AMD.