Refractive error: Genetics

Refractive errors

Refractive error: Genetics. Myopia and hyperopia are the most common types of refractive errors. Refractive errors are the most common cause of visual impairment. The optical defects of the visual system often result in blurred vision.^[1] Myopia, or nearsightedness, is the result of a disproportionate elongation of the posterior segment of the eye. The focal point is located anterior to the retina causing the image that one sees to be out of focus when viewing distant objects.^[2] Hyperopia, or farsightedness, is the result of a relatively short eye. The focal point is located posterior to the retina causing difficulty focusing on objects in close proximity.^[3]

Genetic Risk Factors

The Online Mendelian Inheritance in Man (OMIM) database has listed 261 genetic disorders in which myopia is one of the symptoms.^[4] Myopia may be present in heritable connective tissue disorders such as: Knobloch syndrome (OMIM 267750); Marfan syndrome (OMIM 154700); and Stickler syndrome (type 1, OMIM 108300; type 2, OMIM 604841).^[5] Myopia is present in heritable connective tissue disorders such as: Knobloch syndrome (OMIM 267750); Marfan syndrome (OMIM 154700); and Stickler syndrome (type 1, OMIM 108300; type 2, OMIM 604841).^[6] Myopia has also been reported in X-linked disorders caused by mutations in loci involved in retinal photoreceptor function (NYX, RP2, MYP1) such as: autosomal recessive congenital stationary night blindness (CSNB; OMIM 310500); retinitis pigmentosa 2 (RP2; OMIM 312600); Bornholm eye disease (OMIM 310460).^[7][8] Many genes that have been associated with refractive error are clustered into common biological networks involved in connective tissue growth and extracellular matrix organization.^[9] Although a large number of chromosomal localisations have been associated with myopia (MYP1-MYP17), few specific genes have been identified.^[10]

Fundus of patient with retinitis pigmentosa, early stage

Fundus of patient with retinitis pigmentosa, mid stage

Fundus of patient with retinitis pigmentosa, end stage

A scene as it might be viewed by a person with retinitis pigmentosa EDS07

Environmental Risk Factors

In studies of the genetic predisposition of refractive error, there is a correlation between environmental factors and the risk of developing myopia.^[11] Myopia has been observed in individuals with visually intensive occupations.^[12] Reading has also been found to be a predictor of myopia in children. It has been reported that children with myopia spent significantly more time reading than non-myopic children who spent more time playing outdoors.^[13] Socioeconomic status and higher levels of education have also been reported to be a risk factor for myopia.

References