Genetic markers identified for predicting age-related vision deterioration
As we age, our bodies wear out -- our joints deteriorate, our hair thins, our hearing and vision become increasingly weaker. Some of these effects result from environmental factors, while others are the outcome of genetic predisposition. When it comes to losing our vision, both causes are in play.
Age-related macular degeneration (AMD) causes progressive impairment of central vision, and is the leading cause of irreversible vision loss in older Americans. The macula is a spot in the eye near the center of the retina containing the highest concentration of cone cells. This highly pigmented yellow spot is responsible for central (as opposed to peripheral), high-resolution vision. Whereas loss of peripheral vision may take time to notice, loss of central vision is immediately apparent.
The etiology of AMD is largely unknown, but has historically been linked to age, ethnicity, smoking, hypertension and obesity as implicated risk factors. Scientists at Cambridge Enterprise Limited have turned their attention instead to the significant genetic contribution to developing AMD. In a patent entitled, “Genetic markers associated with age-related macular degeneration, methods of detection and uses thereof,” Professor John Yates of the University of Cambridge discloses a method for identifying an individual who has an altered risk for developing age related macular degeneration through detecting a single nucleotide polymorphism (SNP).
The patented method comprises obtaining a biological sample from the patient, assaying the patient’s DNA and detecting the presence of at least one allele of the complement component 3 (C3) gene comprising a g nucleotide at SNP rs2230199 on Chromosome 19. The invention establishes that identifying nucleotide residues at this location can predict an individual’s predisposition to AMD. The nucleotide residue is identified as normal or variant by comparing it to a normal genomic germ-line sequence of C3 coding sequence.
The SNP used for detecting this predisposition to AMD was identified by genotyping DNA from 1548 individuals, 847 of whom had previously been diagnosed with AMD, and the remaining 701 of whom acted as a control based on their believed absence of AMD.
Measuring this marker in individuals who show no signs of age-related macular degeneration may help to identify those with a heightened risk for subsequent development. This information may provide benefits for insurers, caregivers and employers, and may be of great value in treatment and prevention measures.
No one wants to lose his or her vision, especially if it can be easily prevented. The ability to identify those with a higher predisposition to developing AMD would therefore be highly beneficial. Those with a greater risk could then take steps to prevent vision deterioration, including maintaining a healthy weight, eating foods high in beta carotene and omega-3 fatty acids, exercising regularly, maintaining normal blood pressure levels, not smoking and preventing overexposure to sunlight.
In those patients for whom AMD has already begun, identification of these nucleotide residues would allow for immediate implementation of a treatment regimen, including surgery, chemotherapy and radiation therapy.
This screening for predisposition to AMD is only effective if individuals take the initiative to obtain the testing. We usually don’t think to have our vision tested until we notice a problem with it -- by that time the degeneration has already begun. Thus, this method will only prove beneficial if it is implemented as a regular screening process in middle aged individuals, making it just one more test we have to undergo and pay for.