Two examples of severe hereditary eye disease that often occur in children
Hereditary eye diseases are caused by a coincidental fault in the DNA. In our DNA we have around 20.000 genes. Each gene is a code for a substance, for example a protein, that plays a more or less important part within our body. If there is a fault in a gene that is relevant to the eye function, then an hereditary eye disease can occur. Currently there is no cure for most hereditary eye diseases.
Being diagnosed with an hereditary eye disease comes as an enormous shock, the perspective for the future of the patient and their environment changes radically. Questions arise, such as : How will this disease affect me? Will I become blind? Will I be able to work in my profession?
Retinitis Pigmentosa (RP) is the most common heriditary eye disease, and affects one in 3500 to 4500 persons. This disease usually manifests itself in childhood, but sometimes not until adulthood. People with RP have increasingly more problems with night blindness, tunnel vision, decrease of central vision and eventually become almost completely blind. There are dozens of genes that can cause RP. Currently treatment, such as gen therapy, is being developed for only a small amount of these genetical factors, because the cost of research for these rare diseases are so high. The relatively rare occurrence of these diseases make it difficult to obtain funds to enable the development of new treatments.
The range of vision around the centre of the eye is primarily affected at first in the case of RP, however in the case of Macular Degeneration (MD) it is the centre of the visual field of the macular, “yellow spot” (fovea centralis), which is affected in first instance. Patients with MD experience blurred vision, contrast and colour sensitivity. This leads to problems with reading and distinguishing fine details and recognition of faces.
Macular Degeneration is a general term for a broad scale of eye diseases. The most common variety is the age related Macular Degeneration (AMD). This variety usually occurs after the age of 55 years and is not related to one particular heriditary gen. Around 150.000 persons of The Netherlands are poor sighted or blind due to AMD.
There are also rare, graver varieties of MD that occur at an earlier age (often even in children), that cause severe loss of vision in the central visual field. This is named juvinile MD (JMD). These varieties of JMD are caused by a specific defect gen. The most common varieties of JMD are Stargardt’s disease (around 1/10.000 – 1/15.000 persons), X-related retinoschisis (around 1/20.000 – 1/25.000 persons) and Best disease. There are other rare hereditary diseases of the retina known that cause severe loss of vision, such as Cone Dystrophy and Achromatopsia.