Myopia (near sightedness) is a common refractive disorder due to changes in the axial length (too long), or changes in the refractive power of the eye's optical system (corneal protrusion resulting in steep corneal curvature). As consequence, the image is focused in front of the retina. This results in blurred distance vision unless optical correction is achieved with a refractive device (glasses or contact lenses). A refractive device can provide a more concave surface which reduces the excessive focusing power of the optical system.
Myopia’s prevalence has been rising around the globe and it is estimated that half of the world’s population will be myopic by 2050. In addition, the World Health Organization recognises that myopia, if not fully corrected, is a major cause of visual impairment as increasing myopia can lead to serious eye health problems in the future.
The prevalence of myopia decreases with age, from about 40 percent in adults age 20—59 years to about 20 percent in adults age ≥60 years. The decrease in myopia may be secondary to progressive cataract formation. In contrast to childhood-onset myopia where the degree of myopia tends to worsen rapidly, the degree of myopia stabilises in late adolescence and is subject to a slow rate of myopic change after age of 20.
Myopia risk factors
The development of myopia is associated with higher education levels and intelligence test scores, as well as occupations requiring close-up tasks of high accommodative demand (e.g., reading, writing, computer work). Known causes include:
- Genetic: if one parent is myopic, the risk of the child to be myopic is three times, this increases to 6 times if both parents are short-sighted
- Close work: Increasing evidence suggests that the intensity of close work, that is, sustained reading at closer distance (less than 30 cm) with fewer breaks may be more important than the total hours of near work.
- An association in children between myopia and prolonged reading or reading at close range is well-documented.
- Light exposure: The role of light exposure in the development of myopia is unclear. After adjusting for confounders, children who spend more time in outdoor activities have a lower prevalence of myopia. Persons who are near-sighted have higher serum melatonin levels, suggesting a role for light exposure and circadian rhythm in the myopic growth mechanism.
Myopia is associated with a variety of complications from mild to severe, such as reduced quality of life, symptoms of eyestrain and headache, impaired safety (e.g. driving with uncorrected vision), financial burden (cost of corrective lenses and other medical treatments), beside other more serious complications that can lead to impaired vision and even blindness.
The prevalence of these complications increase with higher degree of myopia. Hence it is important once a child develops myopia to slow it down to prevent these complications.
There are different methods to control myopia and slow its progression. More importantly, we need to work as health professionals in collaboration with families and education system to reduce the incidence of myopia in our society.
General practitioners know what myopia is however, their level of understanding about what is significant myopia, and when you screen for it, would be variable.
Training has changed over the past few decades, and with the continuous education provided by optometrists and ophthalmologists, GPs have an increased level of understanding of the condition, and the methods of treatment and prevention.
Public awareness of myopia is very crucial, knowing your patients potential risk of myopia and taking action before it’s too late can benefit their academic and physical performance, personal growth and overall health.
Once myopia is diagnosed, there are different methods that will help to slow its progression and subsequently reduce the incidence of high myopia.
A useful resource for GPs to provide to patients for the facts on myopia is www.childmyopia.com