A technology first described in the 1990s – OCT – is making the diagnosis and management of retinal eye diseases that much easier.
The eye is a complex sensory organ that enables us to interact visually with our environment. One important component is the retina, which is situated at the back of the eye.
The retina is a multi-layered tissue that “captures” light and “converts” the visual input into electrical impulses that are transmitted to the brain. The brain then reinterprets the impulses as images that we see.
Assessing retinal diseases can be quite a task. It’s not like you are able to detect any problems with the naked eye.
Hence, tools to help diagnosis and track treatment are very important for retinal eye diseases.
One such tool is optical coherence tomography (OCT).
It’s essentially a non-invasive imaging test that “takes” cross-section pictures of the retina in all its glorious detail. Hence, each of the retina’s distinctive layers can be seen.
This is of great help to the eye specialist (ophthalmologist), who can then map and measure the thickness of the respective layers of the retina.
Such measurements can help with the early detection, diagnosis and treatment guidance of retinal diseases such as diabetic retinopathy and age-related macular degeneration.
The technology was first described in the early 1990s, and was initially used mainly in managing eye disorders as it allowed precise imaging of the retina.
However, the technology has advanced so much that it is now being used in some form or other in many other areas of health, including gastroenterology, dermatology, cardiology and oncology, among others.
According to ophthalmologist Dr Jason Ngo Chek Tung, assessing the retina with OCT is a cinch, with no special preparation required.
The scan almost resembles the test for myopia/hyperopia. You are seated in front of the machine, with your chin resting on a support to help keep it motionless. The equipment will then scan your eye without touching it, and the scan does not last more than 10 to 15 minutes.
In Malaysia, the test is available in only a handful of speciality clinics. The price of scanning one eye varies, though it can go as low as RM50.
So, what retinal diseases can OCT look at? Here are a few examples:
This is a common complication of diabetes, and if left untreated, can lead to blindness.
In fact, all those diagnosed with diabetes are at risk of diabetic retinopathy. However, the risk of this complication (as with all other complications of diabetes) can be minimised with good control of blood sugar levels (as well as controlling cholesterol and blood pressure levels).
According to Dr Ngo, continuously high blood sugar levels can damage the network of tiny blood vessels that supply the retina. This eventually damages the retina, hence, the term diabetic retinopathy.
In its early stages, the problem can be managed by simply better controlling glucose levels.
However, in advanced stages, Dr Ngo observes that the patient may need laser surgery to prevent further damage to the eyes.
Central retinal vein occlusion
This refers to a blockage of the main vein in the retina. As a consequence, the pressure results in leakage of blood and fluid into the retina. When this affects the macula, the region of the retina responsible for central vision, vision becomes blurred.
According to Dr Ngo, treatment for this condition includes laser therapy to reduce the swelling due to leakage. The laser is used to seal off the leaking blood vessel that’s causing the swelling.
Other options include injections to help reduce the swelling.
Age-related macular degeneration (AMD)
This condition also affects the macula; hence, it affects central vision. It is the leading cause of severe vision loss for those over 50 years of age.
Effectively, this condition is a result of the macula “breaking down”.
There are two main types: dry and wet.
Dry AMD is due to the build-up over the years of waste products called drusen. This is the most common type of AMD, and results in gradual vision loss over the years.
However, there’s a small possibility that those with dry AMD may develop wet AMD.
Wet AMD is a result of the growth of abnormal blood vessels in the region of the macula, leading to cell damage.
In general, there’s no treatment for dry AMD. However, the Age-Related Eye Disease Study (AREDS) has found that taking high levels of antioxidants and zinc can reduce the risk of developing advanced AMD.
In wet AMD, treatments include laser, photodynamic therapy and certain medicines.
There are quite a few other conditions that OCT can help diagnose and assist in treatment, such as retinal detachment, macular hole and so on.
Suffice to say, with this imaging technique at hand, the process of managing retinal eye diseases is made very much easier.
■ For more information on OCT, email firstname.lastname@example.org.