What is an inherited retinal disease?
An inherited retinal disease (IRD) is a condition caused by a genetic anomaly that leads to loss of vision and in some cases, complete blindness.
There are many types of inherited retinal diseases. Depending on the disease, you may have blindness or vision loss at birth, or it may occur later in life.
What causes them?
The diseases are inherited. This means that you are born with the specific genetic anomaly that results in an abnormality of photoreceptor cells causing the cells in the retina to not work correctly. The retina is the light-sensitive tissue at the back of the eye that senses and transmits light signals to the brain through the optic nerve to form images, enabling people to see.
Researchers have found over 300 genes that cause inherited retinal diseases. Some inherited retinal diseases, such as choroideremia or X-linked retinoschisis are caused by one or only a small number of genes. Other diseases can be caused by many different mutations in many different genes. For example, over 64 genes have been identified that cause retinitis pigmentosa. In addition, for many people, the gene variation that causes their inherited retinal disease has not been identified yet.
Some gene anomalies that cause inherited retinal diseases are more severe than others.
The way that each inherited retinal disease is passed from generation to generation (inheritance) can be different in families. You may have an inherited retinal disease and know a family member with the condition. Or you may be the first one in your family to be diagnosed.
In most people, inherited retinal diseases only affect the eyes. However, some types of inherited retinal diseases are linked with other health issues, such as Usher Syndrome which also affects hearing.
How many people live with an inherited retinal disease?
In Australia, it is estimated that around 16,000 people are living with an inherited retinal disease. They are currently thought to be the leading cause of blindness in working age adults in Australia.
Around 1 in 4000 people or over 2 million people live with an inherited retinal disease worldwide.
Inherited retinal diseases can affect individuals of all ages and genders, and can progress at different rates. Some may be born with or experience vision loss in infancy or early childhood. Some may experience a gradual loss of vision later in life, which may then eventually lead to complete blindness.
Each inherited retinal disease is different. Common symptoms may include:
- Low vision at night, or dim or dark settings
- Loss of central and peripheral vision
- Sensitivity to light, glare and difficulty in bright light
- Farsightedness
- Blind spots
- Colour differentiation difficulties or not seeing all colours
- Uncontrolled eye movements
Obtaining a confirmed diagnosis through genetic testing is the only way to verify the exact gene anomaly(s) that is the underlying cause of an inherited retinal disease.
Further reading
Anatomy of the eye
The eye is one of the most complex organs in the body. There are many parts that make up the eye, all of which are necessary for the eye...
Inheritance Patterns
Some genetically transmitted diseases are the result of a single gene variation however inherited retinal diseases result from a large and as yet unknown number of gene variations.