DNA testing in eye care practice | Optician

Most readers will have heard the recent news stories about DNA testing kits becoming more widely available. A number of kits have been introduced whereby a swab is taken from the inside of the mouth. The saliva and lining remnants are then sent to a lab where the sample is analysed. Variations in the base sequence are known as single nucleotide polymorphisms (SNPs) and the density of SNPs is used as an indicator of disease risk. The nature of the disease will be dictated by the nature and position (within specific genes or ‘stretches’ of the DNA) of the SNP.

Five tests have been developed in the US and have been used to indicate the risk of developing age-related macular degeneration. It was one of these, the 23andMe test, that was responsible for much of the recent publicity because, having been banned (by the FDA) from sale to the public in the US, it has been launched onto the market in the UK.

Conditions such as AMD and dry eye have many variables influencing their expression, and in such a multifactorial disease, recognition of the relevant SNP allows the practitioner to tailor advice pertaining to lifestyle and dietary choices with the aim of reducing the risk of onset. Where a disease has a known inheritance pattern and is directly linked with a mutation of a gene, rather than a whole range of risk factors, then identification of the presence of the mutation makes for a sensitive test in screening for the disease. Granular corneal dystrophies (CGD1 and CGD2, sometimes known as Avellino corneal dystrophy) are autosomal dominant hereditary disorders. These diseases usually develop slowly; however, rate of development and expression will vary according to the individual patient’s age, lifestyle, genetics and living environment. There is currently no distinctive treatment for the disease.


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