Retinal dystrophies are chronic and progressive disorders of visual function. ‘Dystrophy’ means a condition that a person is born with, and ‘retinal’ means relating to the retina.
The retina is located at the back of the eye and is made up of millions of light-sensitive cells called ‘photoreceptors’. When damage to the photoreceptor cells occur, the retina is unable to function properly and struggles to process and transmit sight information to the brain.
The most common retinal dystrophy in Australia is the group of condition called Retinitis Pigmentosa.
Retinitis pigmentosa, or RP, is the name given to a group of inherited conditions of the retina that lead to a gradual progressive reduction in vision.
Loss of side vision (otherwise known as ‘tunnel vision’) and the reduced ability to see at night (otherwise known as ‘night blindness’) are the first notable symptoms of RP. Further down the track, sufferers may experience diminished reading vision (detailed vision), colour vision, and central (‘straight-ahead’) vision.
The expected prognosis of someone with RP is that the condition will continue at a very slow pace, with complete blindness being uncommon, but possible.
RP commonly runs in families and is therefore an inherited condition. It can affect anyone from childhood to their mid-50s, however, it is usually diagnosed in early adulthood. Isolated cases with no family history can also occur.
RP is the major cause of inherited blindness, affecting 1.5 million people worldwide, which equals to 1 in 5,000 people.
Causes and risk factors
There are various inheritance patterns that have been linked to RP, with more than 50 different genetic defects identified, all presenting with different levels of progression and symptoms.
If you have RP in your family, it is recommended that you visit a genetic counsellor to determine you and your family’s risk of the condition occurring.
It is thought that one child is born with RP in approximately every 3,000 births in Australia.
- Loss of side vision (peripheral vision), otherwise known as ‘tunnel vision’
- Loss of central vision (in advanced cases)
- Reduced ability to see at night, otherwise known as ‘night blindness’
- Diminished ability to see in dimly lit conditions
- Diminished ability to judge changes in the levels, such as steps and gutters
- Increased light sensitivity or glare
- Slower to adjust to changes to light sensitivity
To give an accurate diagnosis of RP, a number of tests may need to be performed by an ophthalmologist who has special training in managing retinal or genetic eye diseases. Tests undertaken will establish how well your retina is functioning.
- Visual acuity – a test used to determine ones visual clarity. A patient is asked to read the letters from a chart at a distance. This a common visual test used by many optometrists and ophthalmologists worldwide.
- Visual field – a test used to measure ones field of vision using spots of light projected on a dark background. This test finds any defects in the peripheral (side vision) which gradually decreases over time.
- Electro-retinography (ERG) – a painless test used to measure tiny electrical responses generated by the retina to flashes of light. This is measured via electrodes placed on the surface of the eye.
- Specialised camera is used to take a photograph of the inside of the eye, the images help establish the health of the retina.
- Blood sample may be requested for genetic analysis of known mutations that cause retinitis pigmentosa or similar disorders.
There is currently no cure for RP, and no proven treatments are available to slow the progression of the disease. A number of experimental treatments have been proposed, however the evidence supporting their effectiveness is variable and limited.
A vast amount of work is being done worldwide by various research groups to develop new treatment options for RP.
- Light avoidance – the use of sunglasses have been found to be helpful when protecting the retina from ultraviolet light, however this is only a vision-preserving effect.
- Antioxidants – antioxidant agents may be useful in treating patients with RP but no strong evidence currently exists.
- No smoking – smoking is known to cause oxidative damage to the retina so anyone with inherited retinal disease should avoid or stop smoking all together.
It is recommended having regular checkups with an ophthalmologist to monitor the progression of RP and to check for any reversible causes of vision loss such as cataract or retina swelling.
The Lions Eye Institute also conducts an array of Clinical Trials. You can view these on our Clinical Trials page.
Australian Inherited Retinal Disease Register (AIRD) and DNA Bank
The Department of Medical Technology & Physics at Sir Charles Gairdner Hospital (SCGH) has maintained a register of people affected by Inherited Retinal Diseases (IRDs) and their family members since 1984.
Currently information on 5,500 people affected by IRD, plus DNA from 4,100 people has been collected. This Register includes demographic information and the results of electrophysiological, psychophysical and ophthalmological investigations.
If you know anyone with an inherited retinal disease who may be interested in donating blood or saliva, discussing their family history or being sent a pamphlet on this resource, please contact Tina Lamey, Senior Research Scientist, or telephone (08) 9346 2866.
For more information on the AIRDR, click here.
Further information and support
For further information on RP, including management of the condition, please consult with one of our ophthalmologists.
Please contact The Lions Eye Institute to make an appointment with the appropriate ophthalmologist. A current referral from either a GP, or an optometrist, is required for all appointments.
Australian and international references
Retina Australia – www.retinaaustralia.com.au
RP International – www.rpinternational.org
The British RP Society – www.rpfightingblindness.org.uk
University of Michigan – www.kellogg.umich.edu
State Government of Victoria – www.betterhealth.vic.gov.au