Information on this page is based on that kindly provided by Professor Graeme Black at Manchester Eye Hospital for the RP Fighting Blindness main website.
As you will probably know, RP is a genetic, or inherited, condition and the genetic fault (a ‘mutation’) that an individual RP patient carries may lie in one of a large number of different genes. You may want to know the exact fault that you carry since this may help doctors to predict how vision may change in the future, and also help you to determine the risks of other family members developing the condition.
For genetic testing, you should ask to be referred to regional eye genetic clinics which are run by a combination of ophthalmologists and geneticists who can then arrange for genetic testing to be done. Such testing involves the routine donation of a blood sample (DNA sample) which is then sent to one of the two National Genetics Reference Laboratories in the UK.
Currently testing may not be as easily accessible as it should be to all people with RP throughout the UK. However recent advances in the technology used (January 2012) are improving this all the time and you can make it clear to your GP or ophthalmologist that services are available and that you wish to be referred.
The process of identifying gene faults is known as genetic testing or genotyping.
For some forms of RP there is a real prospect that new treatments based on directly replacing faulty genes may be developed by doctors and scientists in the future. Such ground-breaking developments would make genetic testing essential as it would be necessary to know exactly which gene needed to be replaced.
The number of genes causing RP has until recently made genetic testing very complex and labour-intensive. As a consequence until 2005 no genetic diagnostic service was available to families, but this has changed in recent years.
In January 2012 Professor Graeme Black announced a wider and more efficient genetic testing service for patients with inherited blindness and made the process available to NHS commissioning bodies across the country.
This test now gives many more patients a definitive diagnosis of their condition. It analyses more than 100 genes in parallel, compared to fewer than 10 that older tests can scan, and is based on next generation DNA sequencing technology and advanced computing. It is likely to identify the exact gene flaw causing RP in about 60% of cases and over the coming years this is expected to improve further.
Genetic testing (genotyping) should always be done in conjunction with a consultation with your ophthalmologist and would normally be preceded by genetic counselling. This is to ensure you fully understand the implications of knowing the test results and the life decisions they might influence for you and your family.