Hereditary Eye Diseases

Two examples of severe hereditary eye disease that often occur in children

Hereditary eye diseases are caused by a coincidental fault in the genetica code, 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 a hereditary eye disease often comes as a big shock, and the perspective for the future of the affected person and their environment can change 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

Retinitis Pigmentosa (RP) is the most common hereditary 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 increasing problems with night blindness, tunnel vision, decrease of central vision and may eventually become almost completely blind in some cases. There are dozens of genes that can cause RP. Currently treatments such as gene therapy are being developed for only a small amount of these genetic factors, because the cost of research for these rare diseases is so high. The relatively rare occurrence of these diseases make it difficult to obtain funds to enable the development of new treatments.

Macular Degeneration

In contrast to RP, in which the peripheral vision is primarily affected, people with Macular Degeneration (MD) have their central vision affected first. This is caused by a diseased macula, the central “yellow spot” of the retina (also known as fovea centralis). Patients with MD experience blurred vision, reduced color and contrast vision, resulting for example in problems with reading, distinguishing fine details,m and recognition of faces.

MD is a general term for a broad range of eye diseases. The most common cause is age-related macular degeneration (AMD). This variety usually occurs after the age of 55 years and is not related to one single hereditary gene abnormality. Over 200 million people worldwide are affected by severe AMD.

There are also more rare, severe varieties of MD that occur at an earlier age (often even in children), that cause severe, often rapid loss of central vision. This is named juvenile MD (JMD). These varieties of JMD are each caused by specific genes that are affected. The most common varieties of JMD are Stargardt disease (around 1/10.000 – 1/15.000 persons affected), X-related retinoschisis (around 1/20.000 – 1/25.000 persons affected) and Best disease (around 1/7.500 – 1/15.000 persons affected). There are other rare hereditary diseases of the retina that cause severe loss of vision, such as Cone Dystrophy, Cone-Rod Dystrophy, and Achromatopsia.