Best Vitelliform Macular Dystrophy

Best Vitelliform Macular Dystrophy, often referred to as Best Disease, is a rare genetic eye disorder that primarily affects the macula, the central part of the retina responsible for sharp central vision.

Best vitelliform macular dystrophy (BVMD) is a genetic form of macular degeneration (damage to a part of the eye called the macula) that occurs in about 1 in 10,000 individuals. The physical cause of BVMD is breakdown of the tissue in the retina called retinal pigment epithelium (RPE). The condition gets worse over time, starting with blurred central vision, and possibly leading to complete loss of central vision. Peripheral vision (vision from the sides of the eye) and the ability of the eye to adjust to dark are unaffected. [rx]The age of onset of BVMD can vary. Many individuals with BVMD have symptoms in childhood or early adulthood. BVMD is associated with a harmful genetic change (mutation) in the BEST1 gene. There is no cure for BVMD, although some treatments and medications exist that can minimize the damage caused by breakdown of the RPE including anti-VEGF therapy (medicine used to prevent growth of new blood vessels in the eye), laser photocoagulation (laser treatment used to destroy leaky blood vessels), and photodynamic therapy (a combination of medicine and laser treatment used to get rid of bad eye cells).[rx]

When working normally, the BEST1 gene acts as a gate to help move chemicals between cells in the retina. When this “gate” isn’t working properly, this can cause the build up of fluid and lipofuscin in the retinal tissue. Because BVMD is a progressive condition, there are different stages that are recognized.

• vitelliform stage (stage 1): The stage most commonly seen in new diagnoses of BVMD. In this stage, the macula has the characteristic pocket of yellow-material that can be seen upon examination.
• pseudohypopyon stage (stage 2): The pocket of yellow material moves towards the bottom of the eye. This creates fluid layers where the bottom is the yellow yolk-like fluid and the top is a clear fluid.
• vitelliruptive stage (last stage): The common fluid layers become more spread out in the retina tissue. This spreading can lead to the formation of blood vessels under the macula (choroidal neovascularization) and can significantly impair central vision.[rx]

Types of Best Vitelliform Macular Dystrophy:

1. Classic Type: The most common form of Best Disease, characterized by the accumulation of lipofuscin, a fatty substance, in the macula.

Causes of Best Vitelliform Macular Dystrophy:

The macula is the region of the retina that contains the light-sensing cells necessary for central vision. Individuals with BVMD develop a yellowish material under the macula that resembles an egg yolk (vitelliform means yolk-like). This material eventually breaks up and spreads throughout the macula, leading to a reduction in central vision. Lipofuscin, a chemical made by the body, makes up this yolk-like material.[rx]

BVMD is inherited as an autosomal dominant genetic condition and is usually associated with the mutations in the BEST1 gene. Dominant genetic disorders occur when only a single copy of a non-working gene is necessary to cause a particular disease. The non-working gene can be inherited from either parent. It can also occur as a new gene change in the affected individual. Most individuals affected with BVMD have an affected parent. The chance of passing the abnormal gene from an affected parent to an offspring is 50% for each pregnancy. The risk is the same for males and females.[rx]

1. Genetic Mutation: Best Disease is caused by mutations in the BEST1 gene, which provides instructions for making a protein called bestrophin-1. These mutations lead to the dysfunction of bestrophin-1, resulting in the accumulation of lipofuscin and other changes in the retina.
2. Inherited: It is typically inherited in an autosomal dominant manner, meaning that if one parent carries the mutated gene, there is a 50% chance of passing it on to their offspring.

Symptoms of Best Vitelliform Macular Dystrophy:

1. Blurred Central Vision: The hallmark symptom is a gradual decline in sharp central vision, making it difficult to read, recognize faces, or perform tasks that require fine detail.
2. Distorted Vision: Some individuals may experience distorted or wavy vision when looking at straight lines or objects.
3. Central Blind Spot: A blind spot may develop in the center of the visual field, making it challenging to focus on objects directly in front.
4. Color Vision Changes: Color perception may be altered, with colors appearing less vibrant or distorted.
5. Difficulty with Night Vision: Night vision may be impaired, making it harder to see in low-light conditions.

Diagnostic Tests for Best Vitelliform Macular Dystrophy:

1. Ophthalmoscopy: An eye doctor will use a special instrument called an ophthalmoscope to examine the retina and look for characteristic yellowish deposits in the macula.
2. Electrooculogram (EOG): This test measures the electrical activity of the retina and can help confirm the diagnosis of Best Disease.
3. Optical Coherence Tomography (OCT): OCT provides high-resolution cross-sectional images of the retina, allowing doctors to assess the thickness and integrity of retinal layers.
4. Genetic Testing: A blood sample can be analyzed to identify specific mutations in the BEST1 gene.

Treatments for Best Vitelliform Macular Dystrophy:

There is no cure for BVMD but there are treatment options available that can help reduce the effects of vision loss. For individuals with BVMD who have choroidal neovascularization, anti-VEGF therapy is available to help limit the formation of blood vessels in the macula.

Affected individuals should have regular eye examinations to monitor the progression of the disease. Devices or aids to help with poor vision are beneficial for those who experience significant vision loss.[rx]

If the eye lesions are large enough, sudden injury to the eye or head may lead to bursting of the lesions. People with BVMD should avoid strenuous exercise or high contact activity that may lead to head trauma.

Genetic counseling is beneficial for affected individuals and their families. These specialists can provide information on the genetic causes of certain inherited conditions, counsel on the chance of genetic disease reoccurring in the family, discuss the availability of different genetic testing options, and provide resources related to genetic disease.[rx]

1. Monitoring: Regular eye exams are essential to track the progression of the disease and identify any complications.
2. Low Vision Aids: Devices like magnifiers, specialized glasses, and smartphone apps can help individuals with visual impairment make the most of their remaining vision.
3. Lifestyle Modifications: Protecting the eyes from excessive sunlight and quitting smoking can slow down the progression of the disease.
4. Experimental Treatments: Some ongoing research explores potential gene therapies and drug treatments to target the underlying genetic causes of Best Disease.

1. Anti-VEGF Injections: These medications can slow down the progression of BVMD by reducing the growth of abnormal blood vessels in the eye.
2. Photodynamic Therapy: Laser treatment combined with a light-sensitive drug can help manage abnormal blood vessel growth.
3. Genetic Counseling: If you have BVMD, genetic counseling can help you understand the risk of passing the condition on to your children.

Medications for Best Vitelliform Macular Dystrophy:

While there are no specific drugs to cure BVMD, some medications can be used to manage its symptoms and complications:

1. Vitamin Supplements: Antioxidant vitamins like A, C, and E, along with minerals like zinc, may help slow down vision loss.
2. Anti-VEGF Drugs: Medications like ranibizumab (Lucentis) and bevacizumab (Avastin) can be injected into the eye to reduce abnormal blood vessel growth.
3. Steroids: In some cases, corticosteroids may be prescribed to reduce inflammation in the eye.
4. Supportive Medications: Depending on your symptoms, your doctor may recommend medications to manage related conditions, such as glaucoma or cataracts.

Conclusion:

Best Vitelliform Macular Dystrophy is a genetic eye disorder that affects central vision. While there are no cure-all treatments currently available, monitoring, low vision aids, and lifestyle modifications can help individuals manage the condition. Research continues to explore potential treatments, offering hope for improved outcomes in the future.