Best disease (Best vitelliform macular dystrophy)

Best disease affects the macula, which is the central part of your retina at the back of your eye.

It affects central vision and can make seeing detail more difficult.

There is no treatment for Best disease itself at present. However, a complication called choroidal neovascularisation (CNV) can be treated, so any sudden change in your vision should be checked urgently. Research into gene therapy is ongoing and may lead to a treatment in the future.

This page contains a summary of our information on Best disease. To read our full information, download our factsheet:

Best disease is a type of macular dystrophy and is also called “Best vitelliform macular dystrophy”. Macular dystrophies are inherited eye conditions meaning they are caused by a change in a gene. The altered gene causes changes to the macula.

Best disease only affects the macula. This means it causes changes to your central vision but does not lead to total loss of sight.

Best disease can start to cause changes at the macula between the ages of three and 15, although it does not usually affect vision until later in life.

The sight loss caused by Best disease can take many years to develop. Some people with the condition can continue to read standard sized print into their 40s or 50s or well beyond.

Best disease affects men and women equally. It usually occurs in both eyes, but one eye may be more affected than the other. Sometimes it only affects one eye.

Best disease only affects the eyes. It is not caused by, or linked to, a problem or disease in any other part of the body.

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 find reading small print more difficult, or it may seem that there’s a slight smudge or a small, blurred area in the centre of your vision. Straight lines may look distorted, wavy, or as if there's a little bump in them. People may only notice these changes in one eye.

Some people with Best disease experience light sensitivity (photophobia). Light sensitivity may cause discomfort.

Best disease does not usually affect peripheral vision. As we use our peripheral vision for moving around, most people with Best disease can usually continue to get out and about on their own. For example, someone with Best disease may 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.

You should have your eyes examined by an optometrist (optician) if:

• you notice any difficulty with reading small print (with your reading glasses if you need 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, they may refer you to the clinical team at an eye hospital for further tests. An ophthalmologist (hospital eye doctor) will be part of the clinical team.

How quickly you’ll be seen by the eye hospital will depend on the changes the optometrist has detected. You can ask your optometrist how quickly you should expect to be seen by the eye hospital.

When Best disease is diagnosed, it is difficult to know how much someone’s sight will be affected in the future. How much each person’s vision is affected is variable. Your eye hospital will advise you on how regularly your eye condition should be monitored.

Best disease is a genetic condition. This means it is caused by a change in a gene. The gene change can be inherited from a parent or can, rarely, happen for the first time in a person (a new gene change).

Best disease is caused by a change in a gene called BEST1 (also known as VMD2). Genes carry instructions that help the body work properly. When a gene is changed, it may not give the correct instructions, so the cells may not develop or work as they should.

Normally, the BEST1 gene gives instructions to make a protein called bestrophin-1 in the retinal pigment epithelium (RPE) layer of cells in the retina. The RPE supports and nourishes the retina. The protein made by the BEST1 gene acts as a channel in the cell wall that allows chloride (a type of salt) to move in and out of the RPE cells. This helps to control the movement of fluid and keeps the cells working properly.

If there is a change in a copy of BEST1, these protein channels don’t work as they should, which affects how the RPE cells work and leads to a build-up of waste material under the retina. This is the yellow material seen at the macula. With damage to the RPE, the cells of the retina start to die as they are no longer supported or nourished in the same way.

How are genes inherited?

You have two copies of most genes. You inherit one copy from each of your parents. When you have children, you pass on one copy of each gene to them.

There are several ways a changed gene can be passed down from parents. These are known as patterns of inheritance. Best disease is usually inherited in an autosomal dominant pattern.

Autosomal dominant (AD). This means that only one changed copy of the gene is needed to cause the condition, and usually one parent also has it. However, the condition can be so mild that a parent may not know they have it, and some people who carry the gene change never develop signs of it. Each time that parent has a child, there is a 1 in 2 chance of the child having the condition as well. If a child doesn’t inherit the changed Best disease gene, they cannot pass it on to their children.

Autosomal recessive (AR). More recently researchers have discovered that some changes in the BEST1 gene can be inherited in a recessive pattern. This means that neither parent has the condition themselves, but both parents are “carriers”. When parents are both carriers, every time they have a child, there is a 1 in 4 chance that the child will have the condition. Both parents need to be carriers of the condition for their child to be affected. This is a rarer condition, known as autosomal recessive bestrophinopathy (ARB), which can affect a wider area of the retina than Best disease. Carriers do not usually have any problems with their sight.

There is more information about how hereditary eye conditions are passed down in our Genetics factsheet.

Genetic testing and counselling

If there is Best disease in your family, you may find it helpful to speak with a genetic counsellor, a consultant geneticist, or an ophthalmologist with a specialist interest in genetics.

Genetic testing can help to confirm the gene responsible for Best disease and how it has been inherited. Genetic counselling can help you understand how Best disease has been passed through your family and the chances of passing it on to future children.

Genetic counselling is a free NHS service. You can ask your GP or your ophthalmologist to refer you to your local genetic service.

At the moment, there is no treatment that cures Best disease. The gene that causes Best disease (BEST1) was identified in 1998 and research is ongoing, but this hasn’t yet led to a treatment.

Treatment for complications of Best disease

A small number of people with Best disease may develop abnormal new blood vessels under their macula. This is called choroidal neovascularisation (CNV). There is treatment for CNV which aims to prevent further sight loss.

New blood vessels can be treated with anti-VEGF injections. These injections aim to slow or stop the growth and leakage of the new abnormal blood vessels. In Best disease, CNV often responds well to treatment and some people need only a small number of injections. Vision may improve, although any scarring that has already formed can still affect sight.

Anti-VEGF injections are commonly used to treat CNV caused by Best disease, although there is no specific national guidance for this use. Your ophthalmologist will discuss whether treatment is right for you.

Gene therapy research

Gene therapy is currently being researched as a future treatment for different types of inherited macular dystrophies. Gene therapy aims to add a working copy of the changed gene or, in some approaches, to switch off or correct the changed gene. Working copies of the gene are injected under the retina using a harmless virus to carry the genetic material. The hope is that the affected retinal cells begin to work properly, and the damage is either stopped or reversed.

Even though there is no treatment for Best disease, regular eye check-ups are very important to monitor your condition and its progression.

Monitoring for complications

Ongoing follow up with the hospital eye clinic or optometrist will detect any changes early. This means that if new blood vessels (CNV) develop, they can be treated as soon as possible to help protect your sight. Your optometrist or ophthalmologist will let you know how often you need to have your eyes checked.

If you notice a sudden change in vision in either of your eyes, you should see your optometrist or let your eye clinic know straight away. Even if you have only slight changes in your vision, you should arrange for an eye examination with your optometrist. They are trained to detect any eye problems and, if necessary, can refer you to an ophthalmologist at the hospital.

Diet and lifestyle

There is currently no research to show that diet can help to slow down the progression of Best disease. However, a good diet full of fresh fruit and vegetables can help with eye health in general. Smoking is known to worsen other forms of macular conditions, so it is sensible to stop smoking to protect your general and eye health, although there is no specific research showing that stopping smoking slows Best disease.

Preventing head trauma

There are reports that a blow to the head or eye may trigger bleeding or CNV in people with Best disease. Therefore, it makes sense to take extra precaution in situations where you might get a bang on the head, for example, by wearing suitable protective headgear or eye protection for contact sports, and a helmet when cycling.

Glasses

People with Best disease have a much higher chance of being long-sighted. Long-sightedness means your eyes have difficulty focusing close up. Long-sightedness can be easily corrected with glasses.

Eyes that are long-sighted are often smaller than average, and the drainage angle at the front of the eye can be narrow. This can increase the risk of a type of glaucoma called angle-closure glaucoma, particularly in autosomal recessive bestrophinopathy. Your optometrist or ophthalmologist may check for this. If you suddenly develop a painful red eye with blurred vision, coloured rings (haloes) around lights, a headache or feeling sick, you should get urgent help from an eye casualty department or A&E.

Although glasses or contact lenses cannot correct vision problems caused by Best disease, your optometrist might be able to improve your long-sightedness or short-sightedness with glasses to help give you the best vision possible. Your optometrist will check your glasses prescription at your regular eye examination to make sure your glasses, if needed, are the right strength for you.

It is important to remember that many young people who have Best disease may have good vision for a long time and may only need help when and if their Best disease progresses to the later stages.

With the right support, you can live confidently and independently with your condition. You may not need all this support right now, but you can access further support at any time you need it if your needs change.

There is more information within our full factsheet which is available to download about the following topics:

• Making things easier to see
• Low Vision
• Education
• Driving
• Certification and registration
• Independent living
• Eye care liaison officer (ECLO)
• Charles Bonnet syndrome
• Emotional support and counselling

Connecting with others and support for your eye condition

Sometimes, it can help to connect to people with the same eye condition. The following organisations support people with Best disease or adult-onset vitelliform macular dystrophy:

Macular Society supports people affected by macular conditions. They offer a range of services and also fund research into macular disease. The Macular Society hosts an online Best disease support group a few times a year.

Genetic Alliance UK is an alliance of charities and support groups working to improve the lives of people in the UK with genetic, rare and undiagnosed conditions.

Gene Vision is a resource providing information about rare, genetic eye conditions.

Finding out about research

If you would like to find out more about research into Best disease, the following links may be helpful. You can also ask your eye specialist about any research that may be happening into your eye condition. It’s important to talk to your ophthalmologist first if you are considering taking part in any trial.

Research Opportunities at Moorfields (ROAM)

Eye Research Group Oxford (ERGO)

Be Part of Research

Macular Society

ISRCTN Registry is the UK’s clinical studies register