Myopia is the one of the leading causes of visual impairment and blindness worldwide which affects people of all ages and can reduce the quality of life (Wong HB, 2009).
The prevalence of myopia in school-based children in Singapore was reported to be 29% in 7 year olds, 34.7% in 8 year olds and 53.1% in 9 year olds. For children aged 6 to 72 months, it was reported that myopia prevalence was 11%. A myriad of risk factors like ethnicity, genes, development and growth, environmental factors, habits, as well as existing eye conditions can contribute to causing myopia in children.
What is myopia?
Myopia is also known as short-sightedness, a type of refractive error whereby distance objects appear out of focus. To see things clearly, the structures in our eyes (tear film, cornea, iris, pupil, aqueous chamber, vitreous humour and crystalline lens and extraocular muscles) work together to focus unobstructed light onto the nerves of our retina. Some factors affecting how well we can see include the shape and length of our eyeball (axial length), and the optical power of the eye from the cornea and crystalline lens. A longer axial length due to axial elongation causes light to be focused in front of the eye and not onto the retina, and this leads to myopia. High myopia is associated with eye conditions like myopic maculopathy, retinal detachment and glaucoma to name a few.
Risk factors for childhood myopia
Ethnicity plays a part in the prevalence of myopia especially amongst Asians. Myopia is more prevalent amongst the Chinese compared to Caucasians.
Genetics also play a significant role in causing myopia. If there is family history of myopia, it is likely that the child will be myopic as well. The prevalence of myopia in the child is higher if both parents are myopic as myopia is hereditary.
During development or puberty, a growth spurt in the child could potentially cause increased axial length elongation which leads to onset or progression of myopia.
Eye growth and visual system could be affected in children who are born prematurely. This can result in ocular risk and visual pathway damage. Some of the complications in premature children include under-development of the ocular structures in the eye, retinopathy of prematurity, amblyopia and strabismus which could lead to visual loss and/or refractive error. Myopia is often associated with premature birth.
Some children are born with congenital conditions like congenital cataract or Marfan syndrome while others may develop eye conditions during their developmental phase, like strabismus and amblyopia. These conditions cause poorer development of the visual pathway and abnormal development of ocular structures, which may lead to the onset of myopia.
Environmental and habitual factors play a part in the prevalence of myopia. Studies have shown that prolonged time spent outdoors increases Vitamin D levels and decreases the prevalence of myopia in children. Dopamine, a neurotransmitter and hormone that inhibits axial elongation, is released from the retina when stimulated by increased light intensity. The use of computers and smartphones also contributes to prevalence in myopia as prolonged near work can cause more accommodation required by the eye and therefore stimulates axial elongation.
Symptoms of myopia in children
Children may not be aware that they have myopia, hence it is usually picked up by an adult during an eye check or noticed by a parent. Symptoms of myopia in children include the child reporting blur vision or being unable to read, unable to see objects or recognise faces at far distances which is visible to another person with good vision. A child may cover one eye, tilt their head, frequently rub their eye, squint or strain their eye to see, become unresponsive when called or go closer to the object if they are unable to see well.
Treatment options for childhood myopia
The goal for myopia control is to reduce axial elongation. Taking frequent visual breaks for near work by using the 20-20-20 rule – for every 20 minutes of near work, take 20 seconds to look 20 feet away. Other good habits to cultivate include increasing outdoor activities and less time spent indoors, practising good visual ergonomics by using proper distance of 40 centimetres away from reading materials, ample light at near work and reducing screen time to reduce the onset or progression of myopia.
Other alternatives are myopia control contact lenses like orthokeratology lens or soft contact lens targeted for myopia control, myopia control glasses or the use of atropine eye drops to control accommodation, or a combination of the mentioned methods. These methods can be used prior to the onset of myopia to better control the progression of axial length elongation and myopia.
Working with an eye care specialist for your child’s myopia
A yearly comprehensive eye check-up is recommended for children during schooling years to check for any refractive errors or eye conditions like strabismus and amblyopia. Correction of refractive errors like myopia, hyperopia and astigmatism, should be done promptly such that vision is corrected to reduce progression. Amblyopia and strabismus are eye conditions that could surface due to uncorrected refractive errors, and affect the visual developments of the child. During the developmental phase up till age 8, amblyopia and/or strabismus detected during an eye check-up should be referred to an eye specialist to assess the prognosis of the eye condition.
If your child needs to see an eye specialist for myopia control, please contact Lang Eye Centre at +65 6684 1000 or [email protected].
References & Citation
Wong H-B, Machin D, Tan S-B, Wong T-Y, Saw S-M. Visual Impairment and Its Impact on Health-related Quality of Life in Adolescents. Am J Ophthalmol. 2009;147:505–511.e1.
Saw SM, Carkeet A, Chia KS, Stone RA & Tan DT. Com-ponent dependent risk factors for ocular parameters in Singapore Chinese children. Ophthalmology 2002; 109:2065–2071.
Dirani M, Chan YH, Gazzard G et al. Prevalence of refrac-tive error in Singaporean Chinese children: the strabismus,amblyopia, and refractive error in young SingaporeanChildren (STARS) study. Invest Ophthalmol Vis Sci 2010;51: 1348–1355
Liu Z., Wu D., Huang J. et al., Visual impairment, but not hearing impairment, is independently associated with lower subjective well-being among individuals over 95 years of age: a population-based study, Archives of Gerontology And Geriatrics. (2016) 62, 30–35, https://doi.org/10.1016/j.archger.2015.10.011, 2-s2.0-84952988868.
Senra H., Barbosa F., Ferreira P. et al., Psychologic adjustment to irreversible vision loss in adults, Ophthalmology. (2015) 122, no. 4, 851–861, https://doi.org/10.1016/j.ophtha.2014.10.022, 2-s2.0-84925357345.
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1475-1313.2011.00884.x
https://onlinelibrary.wiley.com/doi/10.1155/2020/4235893
https://onlinelibrary.wiley.com/doi/10.1111/aos.15746
https://onlinelibrary.wiley.com/doi/10.1111/aos.14350
https://onlinelibrary.wiley.com/doi/10.1155/2022/4123470
https://onlinelibrary.wiley.com/doi/10.1155/2021/8915867
https://onlinelibrary.wiley.com/doi/10.1111/j.1600-0420.1997.tb00148.x
https://onlinelibrary.wiley.com/doi/10.1111/aos.14942
https://onlinelibrary.wiley.com/doi/10.1111/j.1755-3768.2009.3325.x
https://onlinelibrary.wiley.com/doi/10.1111/opo.12812
https://iovs.arvojournals.org/article.aspx?articleid=2165363
https://www.nature.com/articles/6702838
https://books.google.com.sg/books?hl=en&lr=&id=nDpG47Tq-S0C&oi=fnd&pg=PA34&dq=myopia+and+genetic+eye+condition&ots=mkMg1iFG1d&sig=bnWYagZ35uPc85vbTFhvRoiOI0Y&redir_esc=y#v=onepage&q=myopia%20and%20genetic%20eye%20condition&f=false
https://iovs.arvojournals.org/article.aspx?articleid=2772539
https://www.aao.org/eye-health/diseases/what-is-marfan-syndrome
