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Current Knowledge on the Hereditary Basis of Myopia

by | Sep 1, 2021 | Manuscripts | 0 comments

Albert Tousif Israfil, M.Optom.

Optometrist and Founder at Advance Eye Care, Assam, India.

 

Vision Science Academy Exclusive

Myopia is one of the emerging global health problems that is pertinent to an abnormal refractive strength of the eye where distant objects appear to be completely blurred in sight. Myopia is quite prevalent in some developed parts of the world while its incidence has been associated with a multitude of etiological factors, such as age and gender, racial, environmental, and genetic factors (Leo & Young, 2011). The latter of course, have been the mainstay of several modern studies focused around myopia.

Myopia and its Genetic Predisposition

The pathogenesis of myopia has been strongly correlated to a plethora of hereditary factors. These statistical results have been mostly derived from twin studies. In this context, several genes located on the chromosomes 5, 6, 10, and 14 have been isolated that contribute to definitive changes in axial length of the eye which in turn, are pathognomonic of myopia (Cai, Shen, Chen, Zhang, & Jin, 2019). Data from several twin studies have revealed that monozygotic twins carry a relatively higher prevalence of myopia-related changes as compared to heterozygotic twins (Dirani, Shekar, & Baird, 2008). These changes involve an aberration of the axial length, intraocular lens power, and/or corneal curvature of the eye.

Animal Models of Myopia

Due to lack of methodologies which can extract samples from human retinal tissue directly, it is essential to utilize animal models to simulate the correlation between genes of interest and the potential development of myopia. In this regard, transgenic mice models have successfully revealed that knock out of a transcription factor such as ZENK/Egr-1 gene results in a longer axial length which suggests that ZENK gene is strongly implicated in the regulation of axial diameter of the eye (Schippert, Burkhardt, Feldkaemper, & Schaeffel, 2007). This example also justifies that apart from the defects associated with structural proteins, most myopic cases stem from an abnormal regulation of the expression of such proteins.

Multiple patterns have been proposed in terms of inheritance for myopia. One study showed that pathological myopia is often inherited as an autosomal dominant trait. Meanwhile, another form of myopia known as Bornholm eye disease, has been speculated to be an X-linked recessive disorder. Furthermore, a total of 4 myopia-related genes (MYP 2-5) have been traced to be of autosomal origin, while MYP 1 is located on the X chromosome (Young, 2009; Zhang, 2015).

Evidence about Multifactorial Significance

In addition to the genetic modulators, environmental factors also play a key role in myopia pathogenesis, thereby indicating its multifactorial nature. It is noteworthy that current data have largely associated myopia with short-distance work such as operating a computer or reading a book as well as higher socioeconomic status. Moreover, factors such as education and genetic predisposition have been found to have a drastic synergistic impact on enhancing the overall occurrence of myopia. This provides us key information regarding the multifactorial status of myopia and other related refractive errors of the eye.

 

References

  1. Cai, X.-B., Shen, S.-R., Chen, D.-F., Zhang, Q., & Jin, Z.-B. (2019). An overview of myopia genetics. Experimental Eye Research, 188, 107778. doi:https://doi.org/10.1016/j.exer.2019.107778
  2. Dirani, M., Shekar, S. N., & Baird, P. N. (2008). Adult-onset myopia: the Genes in Myopia (GEM) twin study. Invest Ophthalmol Vis Sci, 49(8), 3324-3327. doi:10.1167/iovs.07-1498
  3. Leo, S. W., & Young, T. L. (2011). An evidence-based update on myopia and interventions to retard its progression. J aapos, 15(2), 181-189. doi:10.1016/j.jaapos.2010.09.020
  4. Schippert, R., Burkhardt, E., Feldkaemper, M., & Schaeffel, F. (2007). Relative axial myopia in Egr-1 (ZENK) knockout mice. Invest Ophthalmol Vis Sci, 48(1), 11-17. doi:10.1167/iovs.06-0851
  5. Young, T. L. (2009). Molecular genetics of human myopia: an update. Optom Vis Sci, 86(1), E8-e22. doi:10.1097/OPX.0b013e3181940655
  6. Zhang, Q. (2015). Chapter Sixteen – Genetics of Refraction and Myopia. In J. F. Hejtmancik & J. M. Nickerson (Eds.), Prog Mol Biol Transl Sci (Vol. 134, pp. 269-279): Academic Press.

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