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Best disease, also known as vitelliform macular dystrophy, is an inherited retinal degeneration (IRD) which primarily affects the affecting the central region of the retina, called the macula.
The macula contains the cone photoreceptor cells and provides sharp central vision. Best disease is a genetic disease but vision does not usually deteriorate until adulthood.
What are the symptoms of Best disease?
A deterioration of central and detailed vision the most frequent first symptom to arise in Best disease. Distorted vision in which straight lines appear wavy and blurred vision are other common signs of best disease. A yellow substance accumulates under the retinal pigment epithelium (RPE) cell-layer which nourishes and supports the photoreceptor cells and abnormal and excessive accumulation of this yellow substance can cause the cone cells in the macula to degenerate, causing reduced visual acuity.
Best disease most commonly affects both eyes (Binocular) but has also been seen to target only one eye (monocular) or affect one eye more severely than the other. Although the rate of progression of the disease varies between affected individuals, peripheral vision is usually left unaffected and allows people living with the condition to maintain their independence.
What Causes Best Disease?
Best disease is caused by a mutation in the BEST1 gene which makes the Bestrophin-1 protein. Best disease is inherited in an autosomal dominant manner, requiring only one faulty BEST1 gene copy from either parent to cause the disease.
To detect and diagnose Best disease, fluorescein angiograms, optical coherence tomography (OCT) tests and electroretinograms are frequently used. Fluorescein angiograms assess the integrity of the underlying blood vessels beneath the retina. A yellow dye is injected into the person’s arm which flows through the bloodstream and will show up in images of the retina if there is leakage. OCT tests take high resolution images of the different layers of the retina and electroretinograms examine how well rod and cone photoreceptor cells are functioning by measuring how well they respond to different patterns of light.
What treatments are available?
There is no treatment currently available to treat Best disease. However, a small minority of people with best disease have irregular growth of immature blood-vessels called choroidal neovascularisation. Anti-VEGF therapy works by inhibiting this blood-vessel growth and although there is no anti-VEGF specific for Best disease, research is ongoing in this field. A gene therapy to treat Best disease is another possible strategy as there is only one gene known to cause the condition.
It is very important for people living with best disease to have regular eye check-ups because these individuals may still be at risk of developing other kinds of eye problems that affect the general population, some of which may be treatable.