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This study aims to identify and quantify the extent of current variation in service provision of a genetic testing service for dominant and X-linked retinal dystrophies in the English National Health Service (NHS). National audit data (all test requests and results (n = 1839) issued between 2003 and 2011) and survey of English regional genetic testing services were used. Age- and gender-adjusted standardised testing rates were calculated using indirect standardisation, and survey responses were transcribed verbatim and data collated and summarised. The cumulative incidence rate of testing in England was 4.5 per 100,000 population for males and 2.6 per 100,000 population for females. The standardised testing rate (STR) varied widely between regions of England, being particularly low in the North-east (STR 0.485), with half as many tests as expected based on the size and demographic distribution of the population and high in the South-east (STR 1.355), with 36 % more tests than expected. Substantial and significantly different rates of testing were found between regional populations. Specific policy mechanisms to promote, monitor and evaluate the regional distribution of access to genetic and genomic testing are required. However, commissioners will require information on the scope and role of genetic services and the population at risk of the conditions for which patients are tested.

The study of the inherited dystrophies represents one of the greatest success stories of modern molecular genetics. This is a story that began with the description of linkage to part of the short arm of the X chromosome (described as early as 1985 for one of the loci for X-linked retinitis pigmentosa) and the identification of the first gene known to be mutated in adRP (encoding the polypeptide rhodopsin) in 1990. The successful international effort to sequence the entire human genome – the Human Genome Project – represented a landmark collaborative project and its completion, which has enabled the entire human genome to be mapped, further accelerated the ability of scientists to understand the underlying molecular basis of human genetic disease. Consequently, at the time of writing over 200 gene loci and 150 genes have been described underlying human monogenic retinal disorders implying a level of complexity that was unsuspected 20 years ago. This has allowed an entirely new understanding of the genetic basis of this group of conditions. The ‘genetic’ conditions referred to in this text, and within this section, will be monogenic, or Mendelian, conditions. However, it is now recognised that many common conditions have a substantial genetic contribution; the recent delineation of polymorphisms in the complement pathway as key genetic contributors to age-related macular degeneration demonstrates that molecular genetic discoveries have by no means been limited to the Mendelian retinal dystrophies.