Want to learn more about Macular Degenration? Discover the causes and cures of this common disease in the over 50’s.
More than 600,000 people in the UK currently suffer from macular degeneration and this figure will likely rise to nearly 700,000 by 2020, says the National Health Services (NHS). The risk factors for macular degeneration include age, gender and race. More specifically, the middle-aged, the elderly, white and Chinese people are at a greater risk of AMD. At the same time, the condition affects more women than men.
Because the disease mainly affects people age 50 and older, it is commonly referred to as age-related macular degeneration (AMD), which always occurs in both eyes. With that in mind, here is some more information about macular degeneration.
Macular degeneration: An Overview
Macular degeneration is an eye disorder characterized by the deterioration of the central part of the retina called the macula. The macula is responsible for providing clear and distinct central vision.
This means that this eye problem seldom affects peripheral vision. In fact, it usually enhances peripheral vision. With that in mind, a healthy macula is capable of achieving normal eyesight (20/20 visual acuity), with or without contact lenses or corrective lenses.
Some of the common symptoms of AMD include:
Poor depth perception — Depth perception is important because it allows you to see the world in three dimensions, as well as accurately determine the distance between objects. Unfortunately, decrease in vision in either one or both eyes due to AMD may lead to poor depth perception. Loss of depth perception may make you accident-prone and more susceptible to anxiety.
Photostress — To create vision, the light-sensitive receptors in the human eyes (cones and rods) produce chemicals that react to light. However, bright light, such as sunlight, normally depletes these chemicals, causing decrease in vision or dark spots to appear for a short period while the retina replenishes the chemicals. The term photostress essentially describes this brief period of decreased vision. Because macular degeneration damages the retina, it may slow the production of these chemicals, causing the effects of photostress to last much longer.
Blurry vision — A damaged macula is unlikely to attain normal vision (20/20 eyesight) because only a portion of the macula would be able to create vision. It is worth noting that the eye can use the surrounding retina to create vision, but this would likely result in blurry vision because the retina contains far fewer photoreceptors compared to the macula, meaning it is less sensitive to light.
Besides blurry vision, a damaged retina may also result in wavy vision or distortion due to the stretching and misalignment of retinal layers.
Blind spots — While each human eye has a blind spot, macular degeneration often causes the number of blind spots in the eye to increase. Because blind spots lack photoreceptors (rods and cones), they are unable to detect images. Put another way, images that fall inside a blind spot appear to disappear suddenly.
This can make activities such as reading difficult. To try and place an image on the peripheral retina, the patient may turn his/her head or body.
Charles Bonnet Syndrome — Patients who suffer from impaired vision due to macular degeneration may suffer from Charles Bonnet Syndrome. More specifically, such patients may experience complex visual hallucinations when their brains misinterpret blurry visions or distorted images, a condition known as Charles Bonnet Syndrome.
Impaired colour vision — The photoreceptors in the macula are responsible for providing colour vision. This means that, if your macula is damaged, you may develop color vision deficiency. In other words, you may lose your ability to distinguish colours.
Types of Macular Degeneration
Ophthalmologists typically classify AMD as either dry (atrophic) or wet (exudative or neovascular). Atrophic AMD accounts for nearly 90% of all AMD cases. It gradually damages the photoreceptors in the macula, thereby preventing the transmission of visual information to the supporting tissue beneath the macula and the brain. If left untreated, it eventually leads to decreased central vision, blurry vision or even central vision loss.
One of the key identifiers of this disease is the appearance of drusen in the back of the eye. Consisting of a fatty protein and lipids, drusen are essentially multiple, small round yellowish spots.
Ophthalmologists normally use an ophthalmoscope to detect these spots during an eye exam, but the spots are only visible in people age 30 or older. It is important note that drusen does not cause AMD, but it is a risk factor for the condition. For this reason, some patients with drusen may have excellent vision and show no symptoms of AMD. In fact, drusen only become a problem when they grow in size and number.
When this happens, they can interfere with the retina cells in the macula, leading to blurry vision. In the advanced stage of dry AMD, the retina cells usually waste away and die. Ophthalmologists refer to this stage as geographic atrophy (GA) because the regions of atrophy usually look like a map when examined closely. Geographic atrophy can eventually lead to total loss of central vision.
Wet (exudative or neovascular) AMD, on the other hand, accounts for about 10 to 15% cases of AMD. However, while it is less prevalent than dry AMD, it is the severe and usually leads to rapid loss of vision. This condition involves the leakage (exudation) of body fluids including blood, plasma and lipids into the eye, hence the name neovascular AMD or exudative AMD.
This occurs when new blood vessel sprout in the choroid layer behind the retina, a condition called choroidal neovascularization or CNV. If damaged or broken, these fragile blood vessels leak their contents, including blood, plasma and lipids into the eye. This leaking may cause the macula to bulge or shift from its normal flat position, leading to blind spots and loss of central vision. Moreover, the scarring in these blood vessels could also aggravate this condition.
According to a study published in the Ophthalmology journal, choroidal neovascularization (CNV) can be either “classic” or “occult” depending on the visual acuity. Specially, eyes with classic CNV have visual acuity of between 20/250 and 20/400 or even worse than 20/800.
Eyes with occult CNV, on the other hand, have visual acuity of between 20/80 and 20/200. In addition to better visual acuity, occult lesions have less leakage and are not well-delineated.
According to the NHS, the risk factors of age-related macular degeneration include:
Advanced age — Although AMD also affects the middle-aged, studies indicate that people 60 years and older are at a greater risk of AMD compared to people in younger age groups. For instance, one large study found that, while the middle-aged have about a 2% of developing AMD, the risk increased to nearly 30% in people age 75 and older.
Race — White and Chinese people are at a greater risk of central vision loss due to age-related macular degeneration compared to other races.
Family history — People with a family history of AMD (genetic predisposition) are three to four likely to develop AMD.
Gender — Women are more likely to develop AMD compared to men.
Obesity — Obese individuals are twice as likely to develop AMD compared to people with a healthy body weight.
Hypertension and high cholesterol — The National Eye Institute says that individuals suffering from hypertension are nearly twice as likely to develop wet macular degeneration compared to individuals with normal blood pressure readings.
Poor dietary habits — Poor dietary habits, such as consuming artificial fats regularly while shunning fruits and vegetables, may increase the risk of AMD.
Sunlight — Exposure to direct sunlight can damage the macula and cause AMD. This is because, in addition to ultraviolet (UV) rays, the sun also emits blue wavelengths, which are responsible for the damage in this case.
Smoking tobacco — Research indicates that active smokers are two to three times more likely to develop AMD compared to nonsmokers.
Your doctor or optometrist may be able to able to detect AMD before it starts to cause symptoms. For this reason, you should visit the Sight Clinic regularly, preferably every two years, for routine eye tests. The diagnostic process typically involves the following steps and tests:
Your ophthalmologist will start by examining your eyes. More specifically, your ophthalmologist will put eye drops in your eyes to enlarge your pupils.
Once the eye drops take effect, typically after about half an hour or so, the ophthalmologist a magnifying device to examine the back of your eyes where the macula and retina are located with the aim of finding any abnormalities in that area.
To confirm a diagnosis of AMD, the ophthalmologist would need to carry out a series of tests, such as the Amsler grid test.
The Amsler grid test is usually one of the first tests for macular degeneration. To perform this test, your ophthalmologist will ask you to look at an Amsler grid, which is essentially a special grid consisting of horizontal and vertical lines, with a dot located in the middle of the grid.
If your macula is damaged, some of the lines will likely appear distorted, broken or faded, particularly the ones nearest the dot because your macula controls your central vision.
Your response will help your ophthalmologist determine the extent of your macular degeneration.
Your ophthalmologist may need to take pictures of your retina/macula in order to examine it closely for any damage. Additionally, if there is any damage, the pictures will be useful in planning your treatment.
To photograph your retina, your ophthalmologist can use one of the following techniques:
Fundus photography — Thanks to a special camera called a fundus camera, your ophthalmologist would be able to take three-dimensional images of your retina or macula. In other words, the camera would be able to capture the different layers of your retina, making it easier to identify any possible macula/retina damage.
Fluorescein angiography — This procedure would not only produce images of your blood vessels, but also the bloodflow inside them. One of the advantages of this procedure is its ability to differentiate between dry and wet AMD.
To perform fluorescein angiography, your ophthalmologist will inject you with a special dye called fluorescein. Once the dye spreads throughout your blood vessels, including the blood vessels in your eyes, your ophthalmologist will use a special camera to take pictures of your macula and retina. If you have wet AMD, the images will show the dye leaking into your retina.
Indocyanine green (ICG) angiography — Like fluorescein angiography, this procedure uses a dye to identify retina/macula problems. However, the two procedures use different dyes and generally highlight different eye problems.
Optical coherence tomography (OCT) — This procedure uses special rays to scan and produce images of the retina. For this reason, it provides usually provides detailed information about the macula.
For instance, it can reveal whether there is leakage in the retina or not, and whether the size of your macula is normal or abnormal.
The current treatment options for AMD are only to prevent or slow the progress of the condition. In other words, they cannot completely cure the disease. This means the best way to deal with macular degeneration today is through preventative measures.
However, various breakthroughs, such as the implantable telescope, could lead to new and more effective treatment options for AMD. Some of the preventative and treatment options for AMD include:
Cataract surgery — Cataract surgery, particularly laser cataract surgery, was a popular treatment option for age-related macular degeneration before the introduction of VEGF drugs and photodynamic therapy. One of the main disadvantages of cataract surgery is it that it can only be used when there is an abnormal growth of blood vessels in a compact area in the eye, preferably away from the macula/retina.
Anti-VEGF injections — vascular endothelial growth factor (VEGF) is one of the chemicals that promote the growth of new blood vessels in the eyes, which can potentially cause wet AMD. For this reason, anti-VEGF medications are designed to stop the production of VEGF. To administer anti-VEGT medication, an ophthalmologist injects the medication into a patient’s eyes using a very fine needle.
In some cases, the medication can cause the blood vessels in the eye to shrink, resulting in improved vision. However, anti-VEGF injections may also fail to produce any results. Lucentis is a form of Avastin, a drug used to treat colorectal cancer, is one of the most popular and effective Anti-VEGF drugs. The Food and Drug Administration approved Lucentis for the treatment of wet age-related macular degeneration in 2006 following successful clinical trials. During Lucentis clinical trials, nearly 40% of the test subjects reported improved visual acuity of 20/40 or better.
Photodynamic therapy (PDT) — Approved by the FDA in 2010 for the treatment of wet AMD, the ideal candidates for this procedure are patients suffering from “classic” choroidal neovascularization (CNV), especially the ones with new blood vessel growth.
The procedure involves the use of verteporfin (Visudyne), a light-activated drug, which is activated by illuminating it with a low-energy laser beam as it passes through the blood vessels in the eyes. When the drug is activated this way, it produces a chemical reaction that destroys the abnormal blood vessels.
Macular degeneration is the leading cause of vision loss in the UK. This vision condition will affect about 700,000 in the country by 2020, according to the NHS. Age-related mocula degeneration is the most common type of macular degeneration. Currently, no treatment option can cure AMD completely. Some of the treatment options that can manage the disease include Photodynamic therapy (PDT), Anti-VEGF injections and Cataract surgery.