Retinitis pigmentosa (RP) refers to a group of different genetic conditions, all of which cause mottled pigmentation of the retina, with night blindness and variable but progressive loss of visual acuity, sometimes resulting in total blindness. It is not a common disorder: about 1 in 4000 people in the USA is affected.
Causes and risk factors
All the conditions leading to RP are genetic, each with its own pattern of inheritance and individual characteristic symptoms/problems. Many known syndromes are linked to RP, such as:
- Usher’s Syndrome (familial congenital deafness and RP)
- Refsum's disease (heart and nerve abnormalities and RP)
- Bardet-Biedl syndrome (mental retardation; obesity; hypogenitalism)
- Kearns-Syre syndrome (heart block and reduction in eye movements)
- Medullary cystic kidney disease and many more
The most important risk factor is a family history of RP.
Symptoms and their progression
The earliest symptoms noticed - often in late childhood - are decreased vision at night or in dim light. This progresses, until there is loss of peripheral vision, and only "tunnel vision" remains. In severe cases, central vision is also lost, causing total blindness.
Symptoms described by the patient are classical of the condition, and warrant referral to a specialist ophthalmologist for a full examination. These will include:
- Full visual testing of acuityvisual fields and electrophysiological tests
- Full examination of the retina by direct ophthalmoscopy and fluorescein angiography.
- Retinal photography
There is no treatment available for this condition. Some actions may be taken to preserve vision for as long as possible:
- Wearing sunglasses to protect the retina against UV radiation
- Supplemental Vit A palmitate. 15000IU daily may help postpone blindness by many years
- Regular ophthalmologic screening to detect retinal swelling and cataracts, both of which are treatable disorders.
There is steady visual deterioration in this condition, but not all patients end up being totally blind.
Genetic counseling should be offered to patients, to help determine the risk of RP in their offspring.
Reviewed by Dr M J Labuschagne M.B.Ch.B, M Med(Ophth), (OSSA member), University of the Free State, November 2010