– What is Best disease?
– Effects on vision
– The macula
– Detecting Best disease
– The five stages of Best disease
– Regular tests
What is Best disease?
Best disease is an eye condition that affects a tiny part of the retina at the back of your eye, which is called the macula. Best disease can start to cause changes at the back of the eye between the ages of 3-15 although it does not usually affect vision until later on in life.
Best causes problems with your central vision, but does not lead to total loss of sight and is not painful. Best affects the vision you use when you're looking directly at something, for example when you're reading, looking at photos or watching television. Best may make this central vision distorted or blurry and, over a period of time, it may cause a blank patch in the centre of your vision. Best will not usually affect your peripheral (side) vision.
Best disease, also called juvenile Best macular degeneration, juvenile Best disease and vitelliform macular degeneration, is an inherited eye condition which can affect both men and women. It usually occurs in both eyes (binocular) but it may not affect vision to the same extent in each eye. Sometimes it only affects one eye (monocular).
Best disease only affects the eyes so is not caused by, or linked to, a problem or disease in any other part of the body.
The sight loss caused by Best disease can take many years to develop and some people with Best disease can continue to read into their forties, fifties or well beyond.
Adult-onset macular vitelliform dystrophy is a slightly different eye condition to Best disease. In adult-onset macular vitelliform dystrophy there are less changes at the back of the eye, the changes begin much later in life and they do not progress in the same way. Adult-onset macular vitelliform dystrophy does not usually affect sight until around the age of 40 to 60 with very mild or moderate changes in vision. The change to vision can be so small that often it is detected by chance through a routine eye test. In general adult-onset macular vitelliform dystrophy has less impact on vision than Best disease. This guide is about Best disease and not adult-onset macular vitelliform dystrophy.
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Effects on vision
The symptoms of Best disease vary from person to person, but usually the first problems people notice are with their ability to see detail. You may have problems reading small print, or you may find that there is a slight smudge in your sight or that your vision has a small blurred area in the centre. Straight lines may look distorted or wavy or as if there's a little bump in them. People may only notice these changes in one eye.
You should have your eyes tested by an optometrist (optician) if:
- you notice any difficulty with reading small print (with your reading glasses if you wear them)
- straight lines start to look wavy or distorted
- your vision isn't as clear as it used to be.
The optometrist will be able to measure any changes in your vision and examine the back of your eye. If they detect any changes to your macula or any cause for concern they will arrange an appointment with the ophthalmologist (hospital eye doctor) for further tests.
Best affects the macula area of the retina. The macula is a tiny area of your retina which is very important for seeing detail, colour and things directly in front of you.
When the light enters your eye it is focused onto your retina at the back of your eye. The retina includes a number of layers but the most important for vision is a layer made up of cells called photoreceptors. Photoreceptors are cells which are sensitive to light.
The macula, which is a few milimetres in diameter, is a specialised area of the retina that contains a few million photoreceptor cells called cone cells. The macula functions best in bright light levels and allows you to see fine detail for activities such as reading, writing and recognising colours. Best causes your macula to stop working as well as it should.
Away from the central macula is the peripheral retina, composed mostly of the other type of photoreceptor cells called rod cells. They enable us to see when light is dim and provide peripheral (side) vision outside of the main line of sight.
Peripheral vision is the sight you have out of the corner of your eye when looking straight ahead. Best disease does not affect other parts of the retina so does not normally affect peripheral or side vision. Since we use our peripheral vision when we are moving around most people with Best can manage to keep getting out and about on their own. For example, someone with Best may well be able to get to the local bus stop and see a bus coming but find it difficult to see the number on the bus.
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Detecting Best disease
Early signs of Best disease usually develop between the ages of three to 15. In these early stages Best disease doesn’t always have much effect on vision so a child may not notice a sight problem. Sometimes it is picked up at a routine eye examination before it affects vision. This is because an optician or ophthalmologist can see changes in the retina at the back of the eye before vision is affected.
Best disease is increasingly being picked up through screening programmes. This means that the family members of someone who has Best disease can have a genetic test to find out if they might develop the condition.
Sometimes a child may notice a change in their vision and an eye test then confirms they have retinal changes which could indicate Best disease. However, even though someone may have changes to their retina because of Best disease at an early age they may not develop vision problems until much later in life; often over the age of 40 or 50.
The five stages of Best disease
There are five stages to Best disease. These stages can be seen by the doctor when they look at the retina at the back of your eye. None of these stages cause eye pain.
At this stage your macula looks healthy and no change can be seen on examination. There may be subtle changes to a layer underneath the macula but there is generally no effect on vision.
This stage is called the vitteliform stage. At this stage there is a blister on your macula area which looks similar to an egg yolk. Although the doctor can see these changes often there is no effect on vision or very slight changes to vision at this time. Usually this stage occurs between the ages of three and 15 years of age.
This stage is called the pseudohypopynon stage. With this stage some of the yellow matter which causes the egg yolk- like blister can breakthrough a layer under your retina. This leads to a cyst forming under the retina. Again there may be little change in level of sight. This stage is usually seen in the teenage years.
This stage is called the vitelliruptive stage. In this stage the lesion begins to break up and can cause damage to some of the cells in the layers of your retina. At this point you may start to experience changes in your vision. You may start to notice that straight lines look wavy or have problems with reading small print.
This stage is the final stage of Best disease. It is called the atrophic stage. The yellow material which caused the lesions begins to withdraw and disappear. However it leaves behind scarring and damaged cells on your retina. At this stage your sight is more seriously affected and you may find reading difficult.
These are the classic stages of Best disease however some people develop another stage, called choroidal neovascularisation (CNV). This stage develops during the atrophic stage when the eye starts to try to fix the damage to the macula by creating new blood vessels. Unfortunately these blood vessels can lead to more damage and cause further difficulties with vision. However, CNV does not occur in the majority of cases.
You can have Best for a long time without having any sight difficulties. Your sight is not normally affected until stage four or five which may not develop until over the age of 40, although it can occur earlier in someone's late twenties or early thirties. It isn't possible to know exactly when or how much your sight will be affected as it can vary from person to person.
However not everyone with Best has the same kind of disease progression or sight problems. Some people will not progress beyond the early stages of the disease. Many people will have good vision until they reach their fifties and some people will retain reading vision in one eye throughout life. Vision loss is usually extremely slow in people before the age of forty.
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Best disease is a genetic condition. This means that it is caused by a “faulty” gene which may be inherited from a parent or occur as a new genetic variation. It may be inherited as an autosomal dominant trait. Recently the gene responsible for Best disease has been found, but as yet this has not led to any treatment. It has shown, however, that people who have the same fault in this gene can have very different symptoms at different ages, even within the same family. Best disease can be caused by a faulty gene in chromosome 11 (region 11q12-q13) which is also known as VMD2.
What is a “faulty” gene?
All genes come in pairs and you inherit one of each pair from your mother and one of each pair from your father. Your genes determine the many things which make you an individual such as hair or eye colour.
There are a number of ways a genetic condition can be passed through genes to an individual, but they all have to start somewhere in the family tree. These “ways” are also known as modes of inheritance. Best disease is passed on through dominant inheritance.
Dominant inheritance means that a disease is inherited from only one of our parents. When the “faulty” gene lies in its pair with the gene from our other parent it is the dominant one and “switches on” the trait or condition. It is “dominant” over the other “normal” gene inherited from the other parent. When someone who carries the Best gene has a child with someone who does not carry the Best gene there is a 50 per cent chance that it will be passed to a child. If a child does not inherit the Best gene they cannot pass it on to their children.
Best disease is not always passed on directly. For more information on genetic conditions, talk to your ophthalmologist about obtaining a referral to a genetic counsellor at the hospital and your GP about the genetic services in your area.
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If an ophthalmologist suspects you have Best they will initially thoroughly examine your retina.
Your vision will be checked and your pupils dilated to allow the ophthalmologist to look at the macula. Your pupils are dilated with drops that take about 30 minutes to work. They will make you sensitive to light and cause your vision to be blurry. The drops allow the ophthalmologist to see the inside of your eye more easily. The effects of the drops usually wear off in about six hours though sometimes it can happen overnight. It is not safe to drive until the affects have worn off.
The ophthalmologist looks at the inside of your eye using a special microscope called a slit lamp. You place your chin on a rest and the ophthalmologist sits opposite you. The ophthalmologist will ask you to look in particular directions while shining a light into your eye. This allows them to see your retina and any changes that Best may have caused. Although very bright, the light cannot damage your eye.
Sometimes the ophthalmologist can tell you whether they think you have Bests or not from this examination. However, you may need further tests to find out for certain if you have Best. Further tests may include the following:
This test helps the ophthalmologist find out more about your Best disease. The ophthalmologist can usually see the damage to your retina under a slit lamp but they can't see the network of blood vessels underneath it. A fluorescein angiogram is a way of taking pictures of these blood vessels which allows the ophthalmologist to see if there are any changes which could be causing problems.
Before a series of pictures is taken, a yellow dye is injected into your arm which then travels through your bloodstream to your eye. This usually isn't painful but can make some people feel sick. This dye makes the blood vessels visible on the pictures taken. Once the dye has been injected you will be asked to look at a special machine. The machine takes pictures of the back of your eye as the dye is travelling through the blood vessels. You'll experience a series of flashing lights as the pictures are taken, but the test isn't painful. It usually takes about 10minutes.
It is a very common test and very few people have any serious side effects. The injection may give your skin a slight yellow tinge from the dye and it soon passes into your urine, which may also appear a darker yellow than normal (possibly for up to two to three days) but often it fades quicker than that. Some people are dazzled for a while after the flashing lights but most people find the test straightforward.
Optical coherence tomography (OCT)
OCT allows photos to be taken of the back of your eye which provide your ophthalmologist with cross-sectional images of the retina, a bit like a 3D image of the inside of your eye. Dye is not needed for this test. Quite often flourescein angiogram and OCT are both used to obtain a thorough picture of the retina.
ERG is a test which an ophthalmologist uses to assess how the retinal rod and cone cells in you retina are functioning. During an ERG test you are asked to look at a screen which displays patterns of lights including flashes and checkerboard patterns. You are normally lying down or sitting up comfortably during the test. Your pupils are dilated with eye drops and anaesthetic drops will also be put into your eyes to numb them. A vision scientist would then place a small electrode on or near the front of your eyes. This can be a bit like placing a contact lens in your eye. The electrode measures your retina's response to the light patterns. Another electrode is placed on the skin near your eyes.
The test does not cause pain. The only risk of this test is the very rare possibility that the electrode placed on your cornea may graze it and cause a corneal abrasion. If you experience discomfort, redness, or a heat sensation at the front of your eye in the days that follow the test it is important to return to the hospital for an eye check as soon as possible. Corneal abrasions can be well treated when caught early.
The EOG test measures how your retina responds to light and eye movement in response to light. This test can be carried out with or without dilating your pupil. If your pupils are dilated then the test can take longer. If you are light sensitive and concerned about dilation during this test it would be important to discuss this with the hospital in advance. Electrode pads are placed on your skin near to the nasal (nose) side of your eye and on the temporal (hairline) side of your eye. The electrodes are not placed in or on your eye.
You would normally be seated during the test so you are comfortable. You will be asked to look at different lights when they light up. Often this means you are looking back and forth between illuminated targets. The lights will alternate back and forth at different speeds whilst your eyes follow them. Some of this test will take place with the overhead room light dimmed or off, and some of the test will be performed with the overhead room lights on.
There are no risks with this test. Some people made find their eyes can get a tired during the test, and may feel a little achy afterwards, but this quickly wears off.
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Unfortunately there is no treatment for this eye condition at the moment. Although many advances are being made in identifying genes responsible for Best disease, this hasn’t yet led to a treatment.
A small minority of people with Best may develop new blood vessels on their retina. These new blood vessels are medically called choroidal neovascularisation (CNV). These new blood vessels can leak which causes scar tissue and further sight loss. Although treating new blood vessels may not lead to a great improvement in sight, it often helps to prevent further retinal damage from bleeding and scar tissue formation. New blood vessels can be treated with laser and possibly with an anti-vascular endothelial growth factor (anti-VEGF) drug injection.
The term "anti" means against and "vascular" refers to blood vessels. Anti-vascular endothelial growth factor medications (anti-VEGFs) are substances that stop blood vessels from forming or growing by targeting a protein that is needed when new blood vessels form.
Blocking this protein can reduce the growth of new blood vessels, slow their leakage and slow down vision loss. There has not been a large-scale clinical trial researching anti-VEGF treatments for Best related CNV as of yet, but recent small-scale research looks very hopeful with good results. Anti-VEGFs are not yet automatically available on the NHS for people with Best related CNV, but your ophthalmologist would be best placed to decide what treatment is needed in your case.
There is also very positive research for anti-VEGF treatment for adult-onset macular vitelliform dystrophy related CNV.
Gene therapy is currently being researched as a possible treatment for different types of inherited macular dystrophies. It is not available at the moment and it could take a number of years for research to advance further. Gene therapy aims to introduce healthy functioning genes into the retinal cells to encourage them to function properly.
There is no specific research as of yet to show that diet can help to slow down the progression of Best. However, a good diet full of fresh fruit and vegetables can help with eye health in general.
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Even though there is no current treatment for Best it is very important that you receive long-term follow-up care to monitor your condition and its progression. It is also very important to have regular checks with the hospital to ensure that any CNV development can be detected as early as possible to allow treatment if needed.
If you notice a sudden change in your vision, you should always have your eyes examined by an eye health professional. Usually this is an optometrist in the high street. However, if your sight changes very quickly then you can attend the accident and emergency department at your nearest hospital, where an ophthalmologist will be able to check your eyes.
If you have slight changes in your vision then you should arrange for an eye examination with an optometrist (optician). They are trained to detect any eye problems and, if necessary, can refer you to your GP for a further appointment with the ophthalmologist at the hospital.
People with Best disease have a much higher chance of being long-sighted. Long-sightedness means your eyes have difficulty focusing near to. Long-sightedness is usually corrected with glasses. If someone has Best disease and long-sightedness they may also have some difficulties with their visual field (side vision) as well as their central vision.
Glasses or contact lenses cannot correct vision problems caused by Best disease. However, your optician might be able to improve your long-sightedness or short-sightedness with glasses to help give you the best vision possible. Your optician can check your glasses prescription at your regular eye examination to make sure your glasses, if needed, are the right strength for you.
If you have been diagnosed with Best and you notice a sudden change in either of your eyes you should let the hospital know. This is because some people can develop CNV and if this happens sight saving treatment may be possible.
Your ophthalmologist at the hospital should be able to refer you to a genetic counsellor so you and your family can support and have a chance to discuss how the condition may have been passed through your family.
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Being diagnosed with an eye condition can be very upsetting. You may find that you are worried about the future and how you will manage with a change in your vision. We’re here to support you every step of the way, and to answer any questions you may have – just get in touch with our Sight Loss Advice Service.
The Macular Society has local groups which meet throughout the country and also offer a telephone counselling service. Sometimes it can help to talk about your feelings or share with people who may have had similar experiences.
Help to see things better
Best can cause problems with your central vision. However, most people with Best have some vision that they can use everyday and using your vision won't make your Best worse.
There are lots of things that you can do to make the most of the vision you have. This may mean making things bigger, using brighter lighting or using colour to make things easier to see. Ask your ophthalmologist, optician or GP to refer you to your local low vision service, which can provide you with magnifiers to help with reading, advice on lighting and tips on how to make the most of your peripheral vision for everyday tasks to help make the most of your sight.
Local social services should also be able to offer you information on staying safe in your home and getting out and about safely. They should also be able to offer you some practical mobility training to give you more confidence when you are out.
Our Sight Loss Advice Service can also give you practical guidance on living with sight loss, and our Online Shop has products that can make everyday tasks easier.
It is important to remember that many young people who have Best disease may well have good vision for a long time and may only need help when and if their Best disease progresses to the later stages.
Other sources of help
1. Beat the Best – a USA-based online non-profit awareness and support group for people with Best on Facebook.
2. Although there is no specific UK group for people and families affected by Best disease, the Macular Society is the national charity for anyone affected by central vision loss.
3. Genetic Alliance UK is the national charity working to improve the lives of patients and families affected by all types of genetic conditions.
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