What is myopia?
Myopia is a condition in which the eye does not focus properly. It is also known as “short-sightedness” or “near-sightedness.” People with myopia can see more clearly at short distances but have blurred vision at long distances.
Myopia is the most common eye disease in the world. The prevalence of myopia in children varies between countries and ethnic backgrounds, being over 50% in some Asian countries and about 15% in Australia. Unfortunately, the numbers are rising rapidly all around the world.
The economic cost of myopia is huge, estimated at an annual US$250 billion worldwide.
When is myopia diagnosed?
Myopia typically starts in childhood and is usually diagnosed between 5 – 12 years of age. As the child is growing, so does the eyeball. Faster than average growth of the eye can lead to progression (worsening) of myopia until the person is around 20 years of age, or older.
How does myopia affect a child’s vision?
Myopia affects a child’s ability to see both at home and at school, particularly the whiteboard or screen at the front of the classroom.
Children may complain of blurred vision, difficulty focusing, needing to squint, and/or suffering headaches.
What causes myopia?
Myopia occurs when:
- the eyeball is longer than average (most common cause), or
- the cornea of the eye (clear window at the front of the eye) is too steep.
Sometimes myopia is associated with specific conditions that affect the eye and/or the body. In most cases, it is not related to any other associated eye conditions.
There is strong evidence for a genetic component, and children who have myopia often have another family member (usually one or both parents) with the condition. In addition, behavioral and environmental factors have also been shown to be involved.
Time spent outdoors: In both Singaporean and Australian children, total time spent outdoors has been shown to be associated with less myopia. This suggests a protective effect of outdoor activity and exposure to natural light.
Prolonged near work has been associated with myopia, but not consistently and not in all populations. Recent evidence suggests that the intensity of near work, i.e. sustained reading at a closer distance (less than 30 cm) with fewer breaks may be more important than the total cumulative hours of near work.
Recent evidence suggests that the intensity of near work, i.e. sustained reading at a closer distance (less than 30 cm) with fewer breaks may be more important than the total hours of near work.
What are the problems with myopia?
A high degree of myopia is associated with an increased risk of vision loss from complications associated with the abnormally-long eyeball. These include retinal detachment, macular problems, glaucoma, and cataract
Treatment options for myopia
Glasses or contact lenses are prescribed to help the child see better for long-distance. The glasses should NOT be an under-power prescription as there is no evidence of this reduced progression.
Laser refractive surgery, such as LASIK, can be performed in adults once the refractive error has stabilized (eye has stopped growing).
In progressive childhood myopia, near-sightedness often begins in early childhood and progresses as the child grows.
Many parents, who often have high myopia themselves, ask me about why progressive myopia occurs and ways to slow down the progression. In childhood, there is an opportunity to try to slow the progression of myopia, which can reduce the risk of long-term complications.
Multiple treatment options have been attempted and researched:
- Environmental/behavioral interventions
- Low-concentration atropine eye drops
- Special contact lenses or special lenses in glasses
- Orthokeratology (corneal-reshaping technology, rigid contact lenses worn at night)
Eye exercises, vitamins or pills cannot prevent or cure myopia.
All children should have environmental intervention which has been shown to reduce the progression of myopia. These are:
- At least 2 hours of exposure to natural light every day. This can be direct exposure outdoors or even indoors through a window.
- No reading in dim light. It is critical that children do not read books or use a phone, tablet, or another device with the overhead room lighting switched off. This must be emphasized to the child particularly at bedtime.
Atropine eye drops
There is established data in to the use of atropine eye drops to reduce myopia progression. Most of the data comes from studies in Asian populations.
Although the exact mechanism of atropine in myopia control is still disputed, it is thought that it works on receptors on the retina or sclera (white of the eye), reducing stretching of the sclera and therefore eye growth.
Low dose atropine drops are available from compounding pharmacies and instilled once daily into both eyes. At low concentrations, the drop is still effective while side effects are minimized.
It is unclear as to when treatment should be started and for how long it needs to be continued. When used low concentrations, the rebound effect after stopping the drops is minimal.
The most commonly prescribed concentration has been 0.01% drops, based on the ATOM trials. Newer research published in July 2020, from the LAMP trials, suggests that the 0.05% concentration is more effective without any increase in side effects.
Children who are most likely to respond are those whose myopia is related to growth in eye length over time. Eye length can be measured using a test called ‘A-scan’ or biometry. It is important to check the axial length as an objective measure of eye growth prior to and during atropine treatment.
Myopia therapy is best done when children are caught early. Treating children with myopia who already have -5.00 or higher is less likely to work.
Special contact lenses or Special lenses in glasses
Specialized soft bifocal contact lenses with a distance focus in the center appear to be promising, but there are no published randomized clinical trial data on their effectiveness.
Similarly, specialized glasses lenses improve focusing on the peripheral retina and can reduce myopia progression. There are no published randomized clinical trial data on their effectiveness.
Ortho-keratology is treatment aimed at reshaping the cornea to improve vision and reduce myopia progression. Contact lenses are worn at night time which flatten the central cornea. There is some evidence to show that myopia progression is slowed during the period of treatment. There is a small risk of serious corneal infection and permanent scarring with this treatment.
It is recommended that children with high myopia be fully assessed to consider possible associated eye or systemic conditions.
Dr Parth Shah follows an evidence-based treatment protocol, with measurement of the length of the eye and curvature of the cornea at two visits to assess the speed of eye growth and compare this to normal growth rates. Based on a comprehensive assessment, a personalized treatment plan can be made.
Links – WSPOS Myopia Consensus Statement – https://www.wspos.org/wspos-myopia-consensus-statement/