Macular Dystrophy - Causes, Types, Symptoms & Treatment
Macular dystrophy is a rare disease of the eye that causes gradual vision loss by slowly damaging the cells of the macula within the retina. The macula is an area of the retina responsible for visualizing objects that are directly in front of you. Thus, vision damage caused by macular dystrophy makes it difficult to perform simple daily activities like running, driving, or reading.
Causes of Macular Dystrophy
Macular dystrophy is caused by a genetic mutation that prompts the body to produce too much melanin pigment within the cells of the macula. As the pigment builds up it creates a cloudy, grayish-white or yellowish-brown opacity within the corneal stroma, which damages the cells that are needed to see things that are directly in front of you. Although the pigment can expand outwards to the peripheral cornea, most people with macular dystrophy are able to retain their peripheral vision, and are therefore not completely blind.
Macular Dystrophy Types
There are three main types of macular dystrophy, including Stargardt's macular distrophy, Vitelliform macular dystrophy (VTM), and North Carolina macular dystrophy:
Of these three, Stargardt's is the most common type, and is characterized by the formation of physiological waste products that cause the buildup of pigment within the retina. Although Stargardt's typically begins its course during childhood, there is also an adult onset form called fundus flavimaculatus.
Vitelliform macular distrophy is the easiest to diagnose because it is characterized by yellow, oval, egg yolk-like lesions (vitelliforms) of significant size that appear in the center of the macula. Various genetic mutations have been shown to cause VTM, with some forms manifesting during childhood (Best's disease) and some that show up during adulthood with lesions of different shapes and sizes.
North Carolina macular dystrophy is perhaps the rarest type, and is named after a family in North Carolina that was found to have a specific genetic marker that causes this form of the disease. Despite its name, North Carolina macular dystrophy has been positively diagnosed and identified in other areas of the world.
Macular dystrophy is often confused with another more common eye disorder called macular degeneration, which is caused by age-related deterioration of the retinal structures.
Macular Dystrophy Symptoms and Diagnosis
Symptoms of macular dystrophy typically manifest as a decreased visual acuity, particularly within the central range of vision. The gradual degradation of cells in the retina usually leads to optical disorders such as cataracts and refractive errors.
If your physician or ophthalmologist suspects macular dystrophy, they may order special optical tests like fluorescein angiography to check for retinal damage that is characteristic of the disease. Another type of diagnostic test that may be utilized is the optical coherence tomography (OCT) scan, which helps the doctor check your eye tissue for lipofuscin (waste material/pigment deposited from deteriorating eye tissue) within the retinal pigment epithelium (RPE). An electroretinographic (ERG) test may also be used to measure the capacity of your retina's photoreceptors to respond to the presence of light, although this test is mostly used to rule out the possibility of a similar disease known as retinitis pigmentosa.
Macular Dystrophy Treatment and Prognosis
Unfortunately, there is no accepted effective cure for macular dystrophy, so most treatments are aimed at improving the patient's quality of life and slowing down the degeneration of cells within the retina. The first step in seeking treatment is consulting with a retina specialist to determine which type of macular dystrophy you have, what your outlook/prognosis is, and whether you're likely to pass the condition on to your children or grandchildren. Scientists are currently working on advancements in the treatment of macular dystrophy using gene therapies and embryonic stem cell research.