This is the most common form and occurs in 9 in 10 cases. In this type the cells in the RPE of the macula gradually become thinner and degenerate. This layer of cells is crucial for the function of the rods and cones which then also degenerate and die. Dry ARMD is normally a very gradual process as the number of affected cells increases. It usually takes several years for vision to become seriously affected. Many people with dry ARMD do not lose their reading vision completely.
Wet ARMD is also called neovascular or exudative ARMD. It occurs in about 1 in 10 cases. It is likely to cause severe visual loss over a very short time, sometimes a matter of months. Very occasionally, if there is a haemorrhage (bleeding) from a new blood vessel, this visual loss can occur suddenly, within hours or days. In cases of wet ARMD, as well as the retinal pigment cells degenerating, new tiny blood vessels can grow from the small blood vessels in the choroid. This is called choroidal neovascularisation. The new vessels break through Bruch’s membrane and into the macular part of the retina. These fragile new vessels are abnormal and tend to leak blood and fluid. This can damage the rods and cones, and cause scarring in the macula, causing further vision loss.
ARMD is the most common form of macular degeneration and as the name suggests, mainly develops in older people. There are other rare types of macular degeneration which can occur in younger people. Macular degeneration can affect anyone. It is the most common cause of severe visual impairment in the UK. It becomes more common with increasing age, though it is rare in people under the age of 60. If you develop ARMD in one eye, you have about a 60% chance that it will develop in the other eye.
About 1% of people aged 65-75, and about 12% of people aged over 85 have ARMD severe enough to cause serious visual loss. Almost twice as many women over 75 have ARMD compared with men of the same age.
Causes Of Macular Degeneration
In people with ARMD the cells of the RPE do not work so well with advancing age. They slowly fail to take enough nutrition to the rods and cones, and do not clear subsequent waste materials either. As a result, tiny abnormal deposits called ‘drusen’ develop under the retina. Over time the retinal pigment cells and the nearby rods and cones degenerate, stop working and die. This is the dry type of ARMD.
In other cases, something also triggers new blood vessels to develop from the choroid, causing the wet form of ARMD. What prompts this development is not known. One theory is that some waste products which are not cleared from the RPE may stimulate new blood vessels to grow in an attempt to clear the waste.
The exact reason why cells of the RPE stop working properly in people with ARMD is not known. However, certain risk factors may increase the risk of developing ARMD. These include:
- Possibly, high blood pressure (inconclusive evidence).
- A family history of ARMD.
- Sunlight. Though yet to be proven, studies suggest that the retina is damaged by UVA and UVB rays from the Sun.
ARMD seems to be more common in people from Caucasian (white) backgrounds than from other racial groups.
Symptoms Of Macular Degeneration
- The main early symptom is blurred central vision, noticeable even with your glasses. In the early stages of the condition you may notice that:
- You need brighter light when reading.
- Words in a book or newspaper may become blurred.
- You have difficulty recognising faces.
- Colours appear less bright.
- Another early symptom to be aware of is visual distortion. For example, straight lines appear wavy or crooked
- A blind spot may develop in the middle of your visual field. This usually gets bigger over time as more and more rods and cones degenerate in the macula.
- Visual hallucinations (also called Charles Bonnet syndrome) can occur in people with severe ARMD. People see different things, from simple patterns to more detailed images. This can be upsetting but is less of a shock if you are aware that it can be a symptom of ARMD. Importantly, it does not mean you are developing a mental illness. If you do develop visual hallucinations they typically improve within 18 months but in some people they last for years.
ARMD is painless. Symptoms of dry ARMD tend to take 5-10 years to become severe. However, severe visual loss from wet ARMD can develop quicker.
Always see a doctor or optometrist promptly if you develop visual loss or visual distortion.
If the vision of one eye only is affected, symptoms are not always noticeable straight away, as the other good eye often compensates. You are more likely to notice if both eyes are affected. Older people should have regular eye checks and check each eye separately for early ARMD as well as other eye conditions.
Diagnosis Of Macular Degeneration
If you develop symptoms suggestive of ARMD, your doctor or optometrist should refer you to an eye specialist (ophthalmologist). This needs to be done urgently, especially if there is any chance of being wet ARMD.
The ophthalmologist may ask you to look at a piece of paper with horizontal and vertical lines to check your visual fields. If you find that any part of the lines is missing or distorted, then ARMD is a likely cause of the problem. The ophthalmologist will examine the back of your eye with a slit lamp microscope. The ophthalmologist will examine your retinae (plural) through what look like binoculars. Digital photographs can be taken of the retinae. The ophthalmologist will look for the characteristic changes that occur with dry ARMD and wet ARMD.
If wet ARMD is diagnosed or suspected, then a further test called ‘fluorescein angiography’ may be done. For this test a special dye is injected into a vein in your arm. The ophthalmologist will then look into your eyes with a magnifier and take pictures with a special camera. As the dye makes its way through the blood stream, it will show up in the blood vessels in your eyes. The ophthalmologist can see where any dye leaks into the macula from any abnormal leaky blood vessels. This test will show the extent and severity of the condition.
Another test called ‘ocular coherence tomography’ is becoming more commonly used. This is a noninvasive test that uses special light rays to scan the retina, giving very detailed 3D information about the macula, and whether it is thickened or abnormal. This test is useful in determining whether ARMD is the wet or dry form. It is also a good way to assess and monitor the results of any treatment.
- For the more common dry ARMD, there is no specific treatment yet. However, there are certain things that can be done to maximise the sight you do have and to improve your overall eye health. Low vision rehabilitation and low vision services are offered by some hospital eye departments. Information can be found from the Macular Disease Society and the Royal National Institute of Blind People (RNIB). Stopping smoking and wearing sunglasses to protect your eyes from the sun’s rays is important. A healthy diet rich in antioxidants can be beneficial, as may the addition of dietary supplements. Remember that in this type of ARMD the visual loss is often gradual, over 5 to10 years or so.
- For the less common wet ARMD, treatment may halt or delay the progression of visual loss for some people. Newer treatments may even be able to reverse some of the visual loss. Treatments which may be considered include the use of anti-vascular endothelial growth factor (anti-VEGF) drugs, photodynamic therapy and laser photocoagulation.
This is a technique that was developed in the late 1990s. A specialist drug is injected into a vein in the arm. After several minutes the drug binds to proteins in the newly formed abnormal blood vessels in the macula. A light at a special wavelength is shone into the eye for just over a minute. This specialist drug is photosensitive, meaning that when light is shone at the coated blood vessels, it activates to damage and destroy the abnormally growing blood vessels. This technique allows for the abnormal blood vessels to be removed without the risk of damaging the nearby rods and cones nor any normal blood vessels.
Photodynamic therapy is only suitable in some cases. It depends on exactly where the new blood vessels are growing and to what extent. It does not work in all cases but the success rate in treated people is high. Success means that visual loss is halted and prevented from getting worse – it cannot restore any lost vision. Treatment is usually required to be repeated every few months to continue suppressing newly growing blood vessels. The main advantage that this method has over laser photocoagulation is that there is less damage to the normal retina.
This is a technique where a fine laser is directed at the tiny new blood vessels that are forming. This destroys the developing new blood vessels, helping to prevent the condition from worsening. People undergoing this treatment will develop a permanent black or grey patch affecting their vision. Like the above treatment vision loss is restored.
Laser photocoagulation is only suitable for a small number of cases. It depends on exactly where the new blood vessels are growing, as the laser can also damage the rods and cones. New blood vessels growing close to the fovea may not be suitable for this treatment because of the risk of severe visual loss arising from laser damage or scarring due to laser treatment.
Alternative retinal treatments are currently being investigated. Research is being conducted into radiation therapy, other drugs, and different forms of surgery which include grafting techniques. The value of these newer treatments is still unclear. However, with ongoing research treatment may well improve in the near future.
When your vision becomes poor, your ophthalmologist may refer you to a low vision clinic. Staff will provide advice and practical help on how to cope with poor or deteriorating vision.
Help may include:
- Magnifying lenses and bright lamps which may assist reading.
- Being registered as partially sighted or blind. Your ophthalmologist can provide a ‘Certificate of Visual Impairment’ which may entitled you to certain benefits.
- If you are a smoker, try to quit. There are numerous health benefits to quitting. Smoking is a risk factor for many illnesses, not just ARMD.
- Eat a healthy and balanced diet. Try to make sure you get plenty of vitamins that may help in ARMD.
- You should not be driving If you are registered with sight impairment. It is important that you notify the DVLA about your condition. The DVLA website provides detailed guidance on fitness to drive and minimum standards with regard to sight. They includes being able to read a vehicle number plate at a distance of 20 metres, whilst wearing your normal glasses.
Our Appointments Team have a dedicated and caring approach to finding you the earliest appointment possible with the best specialist.
If you do not have a GP, then we have an in-house private GP practice that you can use. Alternatively we can suggest the most appropriate course of action for you to take, given your location and individual circumstance.
If you have medical insurance (e.g. Bupa, Axa PPP, Norwich Union), you will need to contact your insurer to get authorisation for any treatment and, in most cases, you will require a referral letter from your GP.