This web page was produced as an assignment for Genetics 677, an undergraduate course at UW-Madison.
How well can you see?Myopia, or nearsightedness, is the most common human eye disorder, and its prevalence has been reported as high as 70–90% in some Asian countries, 30–40% in Europe and the United States, and 10–20% in Africa [1]. It is characterized by a difficulty to see distant objects because images are fuzzy and out of focus. This occurs because a myopic eye is more elongated than a normal eye, so the light entering in does not focus on the retina, but rather in front of it. Close-up images, however, are clear. Squinting, eye strain and headaches are also associated with this disorder. See the video at the right for a focused explanation of myopia.
|
|
By simply walking down the street, you can see the huge number of individuals affected by this disorder. How many people do you know have to wear glasses?
DIAGNOSIS AND TREATMENT
Figure 1: A standard eye exam includes reading distant letters.
Myopia can be diagnosed with a comprehensive eye exam by an optometrist or opthamologist using a standard set of tests. [3]
This eye disorder can be treated with glasses, contact lenses, or refractive surgery (LASIK). Depending on the severity of your myopia, you may only have to wear corrective lenses for driving or seeing the chalkboard.
Less common treatments for nearsightedness include orthokaratology and phakic IOLs. Orthokaratology involves wearing a rigid, gas permeable contact lens at night that reshapes the cornea of the eye. This shape can be maintained throughout the day so the individual has clear vision without additional corrective lenses. Phakic IOLs are permanent surgical inserts that function like contact lenses. This option is typically for someone who has severe myopia and thin corneas, which puts them at a greater risk for complications during refractive surgery. [4]
This eye disorder can be treated with glasses, contact lenses, or refractive surgery (LASIK). Depending on the severity of your myopia, you may only have to wear corrective lenses for driving or seeing the chalkboard.
Less common treatments for nearsightedness include orthokaratology and phakic IOLs. Orthokaratology involves wearing a rigid, gas permeable contact lens at night that reshapes the cornea of the eye. This shape can be maintained throughout the day so the individual has clear vision without additional corrective lenses. Phakic IOLs are permanent surgical inserts that function like contact lenses. This option is typically for someone who has severe myopia and thin corneas, which puts them at a greater risk for complications during refractive surgery. [4]
a genetic link
Figure 2: A comparison of normal vision
and nearsightedness.
Myopia is a multifactorial polygenic disorder, which means that it has multiple environmental and genetic factors contributing to its characterization. [1] For many years, research has been done to determine the heritability (or likelihood that it will be passed from generation to generation) of this disorder, and finally, Professor Ohad Birk and his team have had a breakthrough. In a collaborative study at the Ben-Gurion University of the Negev and the Dayan Clinical Genetics Wing at the Soroka University Medical Center, members of the local Bedouin tribe have been used as a model to find a gene linked to this disorder. [2]
They discovered that LEPREL1, a gene on chromosome 3, contributes to nearsightedness. It encodes an enzyme essential for the final modification of collagen in the eye, and when this gene is mutated, this enzyme cannot function properly. Because collagen makes up 80% of the eye [5], the imperfect protein causes the eye to elongate more than usual. When light passes through, it focuses in front of the retina as opposed to focusing directly on it.
There's much more to nearsightedness than having to wear corrective lenses. This eye disorder is connected to higher incidence of premature glaucoma, macular degeneration, retinal detachment and cataracts. [2] By studying this gene, we can learn more about how to correct and even avoid his disorder at the most basic, molecular level.
See the "GENE" page to learn more!
They discovered that LEPREL1, a gene on chromosome 3, contributes to nearsightedness. It encodes an enzyme essential for the final modification of collagen in the eye, and when this gene is mutated, this enzyme cannot function properly. Because collagen makes up 80% of the eye [5], the imperfect protein causes the eye to elongate more than usual. When light passes through, it focuses in front of the retina as opposed to focusing directly on it.
There's much more to nearsightedness than having to wear corrective lenses. This eye disorder is connected to higher incidence of premature glaucoma, macular degeneration, retinal detachment and cataracts. [2] By studying this gene, we can learn more about how to correct and even avoid his disorder at the most basic, molecular level.
See the "GENE" page to learn more!
References
[Header Image] From Thomas Hawk's Flickr account. 31 Jan. 2006. Glasses [Photograph] Retrieved from
http://www.flickr.com/photos/thomashawk/2354086423/lightbox/
[1] Fredrick, Douglas. 18 May 2002. "Myopia. Clinical Review." BMJ 2002; 324 doi:http://dx.doi.org/10.1136/bmj.324.7347.1195
[2] American Associates, Ben-Gurion University of the Negev. 2 Sep. 2011. "Researchers identify gene that leads to myopia (nearsightedness)." ScienceDaily. Retrieved 24 Jan 2013 from http://www.sciencedaily.com/releases/2011/09/110901135018.htm
[3] http://www.allaboutvision.com/eye-exam/expect.htm
[4] http://www.allaboutvision.com/conditions/myopia.htm
[5] Kirschbaum OD, Stephanie, Curry, S.R., Buckley, Maggie. 19 Aug. 2007. "Ehlers-Danlos Syndrome- The Role of Collagen in the Eye." Retrieved 4 Feb. 2013 from http://www.newtons-online.net/histories/ehlers%20danlos%20eyes.pdf
http://www.flickr.com/photos/thomashawk/2354086423/lightbox/
[1] Fredrick, Douglas. 18 May 2002. "Myopia. Clinical Review." BMJ 2002; 324 doi:http://dx.doi.org/10.1136/bmj.324.7347.1195
[2] American Associates, Ben-Gurion University of the Negev. 2 Sep. 2011. "Researchers identify gene that leads to myopia (nearsightedness)." ScienceDaily. Retrieved 24 Jan 2013 from http://www.sciencedaily.com/releases/2011/09/110901135018.htm
[3] http://www.allaboutvision.com/eye-exam/expect.htm
[4] http://www.allaboutvision.com/conditions/myopia.htm
[5] Kirschbaum OD, Stephanie, Curry, S.R., Buckley, Maggie. 19 Aug. 2007. "Ehlers-Danlos Syndrome- The Role of Collagen in the Eye." Retrieved 4 Feb. 2013 from http://www.newtons-online.net/histories/ehlers%20danlos%20eyes.pdf