Blurry vision is never fun, especially if you have a fast-paced lifestyle and need to fetch the kids, buy some dinner and finish the big proposal due for the next day. In the past, your eye-care specialist used to put drops in your eyes before checking for underlying problems with your vision.
Most people who wear glasses have had to experience getting those nasty eye drops at some stage of their lives. The effects of the drops can remain several hours after the test and patients normally complain of blurry vision and/or light sensitivity. The discomfort does not stop there. Normally, you will have to get someone to drive you back home, a challenging prospect if you live a busy life.
Fortunately, technology has advanced with the introduction of optical coherence tomography (OCT) in the 1990’s. The science and engineering of OCT have developed substantially since then, with more than ten large manufacturing companies in the USA working to improve the technology. OCT has reformed the treatment of eye diseases on a global basis and it is now routinely used to make clinical decisions about treating patients with blinding diseases such as macular degeneration, diabetic retinopathy, and glaucoma.
What is it?
Optical Coherence Tomography, or OCT, is a technique used by eye-care professionals to obtain images of the inside of the eye. The resolution of these images is very high, making it the best imaging device in the medical field. It works like a typical ultrasound device, but instead of sound, it uses light that reflects from the tissues in your eye. An optical beam is directed at the eye tissue and the light that is reflected from the different layers are collected and an image is processed. The technology is so good that it can take cross-sectional pictures of the different layers in your eye and provide the doctor with 3D images to help him or her to make better diagnoses of patients.
OCT imaging is extremely safe and can be routinely performed on patients of any age. Another advantage is that OCT does not require direct contact with the eye and does not usually require dilation of the pupil to acquire images, although this may still be required depending on individual circumstances. This is great news for those of you that really dislike the discomfort of blurred vision that dilated pupils give.
How is the test performed?
It is a very simple procedure and totally painless. This test is performed by your eye-care professional who will stay with you throughout the test. It typically takes 5 to 10 minutes to complete.
You will be asked to place your chin on a support in front of the instrument with your forehead pressed against it.
You will be told to stare at a fixed point so that your eyes remain still.
The consultant will tell you to avoid blinking for short periods of time while the images are taken.
During the test, you will see a series of lights moving across your field of view.
Several scans may be performed for each eye as required.
What does it test for?
OCT scanning is used to diagnose the following diseases:
Glaucoma
This disease causes damage to your optic nerve (located in the retina) and may cause vision loss. It usually happens when fluid builds up in the front of your eye and causes increased pressure in your eye. With all types of glaucoma, the nerve linking the eye to the brain is damaged, usually due to the pressure. The most common type of glaucoma is called open-angle glaucoma. It often has no symptoms other than slow vision loss. Angle-closure glaucoma is rare, but it is very serious. It normally is accompanied with pain, nausea and sudden visual interference. In general, untreated glaucoma can cause blindness, but it normally progresses slowly and can be treated with special eye drops to lower the pressure caused by the fluid. The important thing is to have it diagnosed early.
Diabetes
People with diabetes can have an eye disease called diabetic retinopathy. High blood sugar levels cause damage to blood vessels in the retina. The damage ranges from leaking, closing of the vessels or the formation of new abnormal blood vessels. At first, diabetic retinopathy may cause no symptoms or only mild vision problems. Eventually, it can cause blindness. The condition can develop in anyone who has type 1 or type 2 diabetes. The longer you have diabetes and the less controlled your blood sugar is, the more likely you are to develop this eye complication. Diabetic retinopathy symptoms may include spots or dark strings floating in your vision (floaters), hazy and inconsistent vision, reduced color vision or complete vision loss.
Macular hole
The macula is the most sensitive part in the retina and is responsible for sharp, central vision. It is the macula that is responsible for your pinpoint vision, allowing you to read, drive, and recognize faces and road signs. It is made up of millions of light-sensitizing cells and helps to turn light into electrical signals that are sent to the brain, which in turn transforms it into the images we see. Damage to the macula normally involves blurring in the center of vision. A macular hole is when a tear or opening forms in your macula. As the hole forms, things in your central vision will look blurry, wavy or distorted. As the hole grows, a dark or blind spot appears in your central vision. A macular hole does not affect your peripheral (side) vision.
Macular pucker
The macula is supposed to be positioned flat against the back of your eye. Macular puckering is when wrinkles or bulges form on the outer side, releasing the contact with the back of the eye in some areas. It also causes blurred central vision.
Macular edema
Macular edema develops when blood vessels in the retina starts to leak. The macula swells because of this, blurring your vision.
Age-related Macular Degeneration (AMD)
Age-related macular degeneration (AMD) is a leading cause of visual impairment in patients over 60 years of age in developed countries and it is estimated that 12 to 13 million people in the USA will have the disease by 2020. There are two types of AMD. Dry AMD is when parts of the macula become thinner with age. Tiny clumps of protein, called drusen, starts to grow and show up as yellow spots on the images. You slowly lose central vision. Most people develop some very small drusen as a normal part of aging. The presence of medium to large drusen may indicate that you have AMD.
Wet AMD is when new, abnormal blood vessels grow under the retina. These vessels may leak blood or other fluids, causing damage to the macula. Many people don’t realize they have AMD until it is too late – when their vision starts to become blurry.
Vitreous traction
The gel-like material that fills the space within the eye between the lens and the retina is encapsulated in a thin shell, called the vitreous cortex. This cortex usually sticks perfectly to the retina in healthy eyes. As the eye ages, the vitreous cortex can slowly start to detach from the retina, causing blurry vision.
Cancer
A dark spot at the back of the eye may indicate a cancerous growth in the retina. If caught early, melanomas can be treated before they cause serious damage and travel to other areas of the body through the bloodstream.
What Are the Benefits of OCT?
Retinal imaging allows eye care practitioners to diagnose eye diseases that they couldn’t before. The test itself is painless and the results are easy for doctors to interpret. Images are stored and can be compared with scans you had when you were younger, giving the doctor the opportunity to check that there are no structural changes to the eye.
OCT is not just the optical health diagnostic tool of choice; it can also help to detect other diseases at an early stage. The Centre for Disease Control and Prevention released some alarming figures in 2013. According to them, 360,000 people died that year of heart attacks - that is almost 1,000 people per day. Hypertension is the main culprit since 7 out of 10 of these deaths reported were of people who had high blood pressure. Furthermore, according to a large study involving 154,000 adults across 17 countries in 2013, as many as 50% of people suffering from high blood pressure (hypertension) don’t even know it.
Here’s the point: signs of high blood pressure are often detected first in the eye. The old adage that the eyes are the windows to the soul is not true anymore. Eyes are, in many cases, windows to your health too. Make sure you visit your eye-care practitioner regularly. Prevention really is better than cure and OCT scanning is the one tool that provides the best diagnoses by far.