By Alessio Spiga, optician optometrist and student of SAERA.
Introduction
Myopia, also called nearsightedness, is a common problem where light rays passing through the eye are focused before they reach the retina. It is the most common refractive error of the eye, and it has become more prevalent in recent years. Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye and it can also be caused by the cornea and or lens being too curved for the length of the eyeball. In some cases, myopia is due to a combination of these factors. It typically begins in childhood and you may have a higher risk if your parents are nearsighted. In most cases, nearsightedness stabilizes in early adulthood but sometimes it continues to progress with age.
Sometimes myopia can be so progressive and severe it is considered a degenerative condition. Degenerative myopia is a relatively rare condition that is believed to be hereditary and usually begins in early childhood. About 2 percent of Americans are afflicted, and degenerative myopia is a leading cause of legal blindness. In malignant myopia, the elongation of the eyeball can occur rapidly, leading to a quick and severe progression of myopia and loss of vision. People with the condition have a significantly increased risk of retinal detachment and other degenerative changes in the back of the eye, including bleeding in the eye from abnormal blood vessel growth. Degenerative myopia also may increase the risk of cataracts. Surgical treatment for complications of degenerative myopia includes a combination drug and laser procedure called photodynamic therapy that also is used for the treatment of macular degeneration.
Studies in different environments
A recent study by the National Eye Institute (NEI) shows the prevalence of myopia grew from 25 percent of the U.S. population (ages 12 to 54) in 1971-1972 to a whopping 41.6 percent in 1999-2004 (‘Increased prevalence of myopia in the United States between 1971-1972 and 1999-2004. Archives of Ophthalmology. December 2009’).
Though the exact cause for this increase in nearsightedness among humans is unknown, many eye doctors feel it has something to do with eye fatigue from computer use and other extended near vision tasks, coupled with a genetic predisposition for myopia.
With more and more people getting nearsighted these days, there is a lot of interest in finding ways to control the progression of myopia in childhood.
A number of different techniques have been tried including fitting children with bifocals, progressive lenses and gas permeable contact lenses with mixed results.
Recently, researchers in New Zealand have reported encouraging outcomes from specially designed “dual focus” soft contact lenses for myopia control in nearsighted children. The experimental lenses have significantly less power in the periphery of the lens compared to the center, and it is thought that this “peripheral defocus” may reduce the tendency for greater lengthening of the eye that leads to progressive myopia. In a study published in 2011, the researchers found that in 70 percent of nearsighted children (ages 11 to 14) who wore the experimental lenses in one eye and a standard soft contact lens in the other, myopia progression was reduced by 30 percent or more in the eye wearing the dual focus contact lens (‘Effect of dual-focus soft contact lens wear on axial myopia progression in children. Ophthalmology. June 2011’).
Though dual focus contact lenses for myopia control are not yet available in the United States, research is ongoing to evaluate the effectiveness of the lenses on a larger population of children.
Certain topical drugs can be used to slow the progression of myopia, but they cause a reduction in the ability to see up close and they also cause the pupil to dilate and therefore increase light sensitivity.
The use of special bifocal contact lenses and lenses that reshape the cornea have both demonstrated some ability to slow the development of myopia but are not yet approved for that use.
Also, a recent pilot study found that an oral medicine called 7-methylxanthine (7-mx) was effective in slowing the elongation of the eye in nearsighted children ages 8 to 13. Studies of this type might eventually lead to an effective medical treatment for degenerative myopia (‘Systemic 7-methylxanthine in retarding axial eye growth and myopia progression: a 36-month pilot study. Journal of Ocular Biology, Diseases, and Informatics. December 2008’).
Several studies have demonstrated that taking part in outdoor activities for some portion of the day results in less myopic development. One theory is that the ambient outdoor light is a key factor in less myopic development.
Another study was to investigate the effect of outdoor activity during class recess on myopia changes among elementary school students in a suburban area of Taiwan. The children of one school participated in the interventions, whereas those from the other school served as the control group. The interventions consisted of performing a recess outside the classroom (ROC) program that encouraged children to go outside for outdoor activities during recess. The control school did not have any special programs during recess (‘Outdoor Activity during Class Recess Reduces Myopia Onset and Progression in School Children, Pei-Chang Wu, Chia-Ling Tsai, Hsiang-Lin Wu, Yi-Hsin Yang, Hsi-Kung Kuo, 2013’). The results show that 571 students were recruited for this study, of whom 333 students participated in the interventional program, and 238 students were in the control school. At the beginning of the study, there were no significant differences between these 2 schools with regard to age, gender, baseline refraction, and myopia prevalence (47.75% vs. 49.16%). After 1 year, new onset of myopia was significantly lower in the ROC group than in the control group (8.41% vs. 17.65%; P<0.001). There was also significantly lower myopic shift in the ROC group compared with the control group (−0.25 D/year vs. −0.38 D/year; P = 0.029). The multivariate analysis demonstrated that the variables of intervention of the ROC program and higher school year proved to be a protective factor against myopia shift in nonmyopic subjects (P = 0.020 and P = 0.017, respectively). For myopic subjects, school year was the only variable significantly associated with myopia progression (P = 0.006), ( Wu et al., 2013).
Conclusions
Outdoor activities during class recess in school have a significant effect on myopia onset and myopic shift. Such activities have a prominent effect on the control of myopia shift, especially in non-myopic children.
Furthermore, is possible to say that, specially in the age of the development, to spend more time outdoor and to read books and newspapers on paper are a healthy training for a right focus in natural light conditions.
If children spend more time outdoor the risk of myopia is reduced because the dopamine, a neurotransmitter also located in the retinal cells and activated proper under the effect of natural light, plays a fundamental role in the transmission of the images to the brain; it also seems that the dopamine would be able to avoid the excessive growth of the eye from birth to 25 years.
Today one child on five is short-sighted, in 2025 it will be one on two if prevention systems are not used. This is what results from a research on 11 thousand Taiwanese students (‘I difetti della vista’, Lucio Buratto, Centro Ambrosiano Oftalmico, 2012).
In my opinion, with modern technology, different environments of work, different lifestyle compared to the past it is necessary to prevent ocular and general health, using lenses with anti-reflection for blue light, doing breaks during up close activity, to limit the hours of daily use of electronic devices, to spend more time outdoors and to educate mostly children to protect their eyes.