What is Best Disease?
Best disease, also known as vitelliform macular dystrophy, is an inherited form of macular degeneration characterized by a loss of central vision.
What are the symptoms?
Best disease affects the macula, the central part of the retina responsible for fine visual detail and color perception. The retina and its component photoreceptor cells are essential to vision as they convert light into electrical impulses and then transfer these impulses to the brain via the optic nerve.
Although the age of onset for those with Best disease can vary, it is usually diagnosed during childhood or adolescence. In the initial stages, a bright yellow cyst (fluid-filled sac) forms under the retinal pigment epithelium (RPE) beneath the macula. Upon examination, the cyst looks like a sunny-side-up egg. Despite the presence of the cyst, visual acuity may remain normal or near normal (between 20/30 and 20/50) for many years. Peripheral (side) vision usually remains unaffected.
In many individuals with Best disease, the cyst eventually ruptures. Fluid and yellow deposits from the ruptured cyst spread throughout the macula. At this point the macula has a scrambled egg appearance. Once the cyst ruptures, the macula and the underlying RPE begin to atrophy (degenerate) causing further vision loss. As a result, central vision tends to deteriorate to about 20/100 later in life. However, Best disease does not always affect both eyes equally. Many individuals retain useful central vision in one eye with a visual acuity of about 20/40 in the lesser-affected eye.
In some cases, Best disease does not progress far enough to cause significant central vision loss. However, retinal specialists can still detect the disease using sophisticated diagnostic tests that measure the function of the RPE and the retina. Individuals with Best disease are also often farsighted. Farsightedness can be corrected with glasses.