08 February, 2021

Spotlight on Myopia

The World Health Organisation estimates that short-sightedness, or myopia, affects approximately 30 per cent of the world’s population with an expectation that figure will rise to 50 per cent by 2050.
According to the Brien Holden Vision Institute, the number of Australians with myopia is expected to increase by a staggering 5 times from around 4 million today to 22 million by 2050.
It is estimated that the cost of vision disorders to our economy is already estimated at $16.6 billion dollars per annum – that’s a massive $45.5m per day or $1.9m per hour. Now, imagine the cost on the health system if the myopia rate increases five-fold.

What is Myopia?

Myopia (also known as short-sightedness) is a common eye condition that causes distant objects to appear blurry, which is corrected with prescription glasses, contact lenses or laser surgery.

What causes Myopia?

Scientists are still trying to understand how myopia develops and progresses.
It occurs when the eyeball is too long or the eye’s focusing power is too strong. When light enters the eye, it is bent by the cornea (the clear layer at the front of the eye) and the lens. If you have normal vision, the light waves are brought into focus right on the retina, the layer at the back of the eye. If you are myopic, the light waves from distant objects focus in front of, rather than on, the retina.

Illustration showing the differences between normal vision and myopia. Myopia causes light to focus in front of the retina instead of on the back of the eye, causing distant objects to appear blurry.

 

Myopia usually appears in the pre-teen years and continues to increase into early adulthood.
Myopia is becoming more common. Researchers believe that its increased prevalence is linked to less time spent outdoors and more time spent focusing on near objects, i.e., reading, computers and devices. A nationwide study in Taiwan found that after-school study programs with lots of near work were associated with an increased likelihood of myopia among children ages 7 to 12. A study of Chinese schoolchildren found that increased time spent working with the eyes focused on an object less than 20 cm’s away was associated with myopia. Researchers in Ireland found that greater than three hours of screen time per day increased the odds of myopia in schoolchildren, and investigators in Denmark found that the risk of myopia approximately doubled in Danish teenagers who used devices for more than six hours per day.

Why Outdoor Time Matters?

Research suggests that spending time outdoors may be able to slow the onset and progression of myopia.
In Taiwan, first grade students at schools with programs designed to increase their outdoors time to 11 hours or more each week had less progression of myopia over one year compared to their peers. Similarly, in China, researchers found that adding 40 minutes of outdoor activity a day at school reduced the development of myopia in six-year-old children over the next three years.
It is still not clear why outdoor time protects against myopia, or why close-up work could make it worse. One theory is that light intensity and time spent outdoors regulates the release of dopamine in the retina, which controls the growth of the eye.
Other theories centre on how viewing distances impact where the light is focused on the retina; shorter viewing distances indoors may promote abnormal growth of the eye.

How can I tell if I’m myopic?

If you are myopic, distant objects will appear blurred when you look at them. It can be hard to tell, but you might notice that other people can see distant objects more clearly than you can.
Children might have difficulty reading the board in class or be reluctant to play outdoor sports. Your child might squint to see things at a distance or they might sit very close to the television.
Diagnosing Myopia

An eye test allows the optometrist to diagnose myopia, which involves looking at a letter chart. The optometrist will then use lenses to determine your prescription, which is the power required to focus light onto the retina. Myopia is corrected by minus powered lenses which shifts the focal point back onto the retina.
If you feel that you or your child might be myopic, see your optometrist for an eye test. Children should have their vision checked when they start both primary and secondary schools.

Treatment of Myopia

Myopia has historically been corrected with prescription glasses. Contact lenses are also an option; there are soft contact lens options that are worn during the day or rigid lenses that are worn only at night, which is known as orthokeratology. Orthokeratology or Ortho-K involves inserting lenses in the eyes before sleep, which re-shapes the eye (flattening the cornea), such that on removal in the morning you can see clearly without the need for glasses. Orthokeratology and peripheral defocusing soft contact lenses have both been shown to reduce the progression of myopia by approximately 50%. Laser refractive eye surgery is also a treatment option, but is only appropriate for adults.

Finally, even if you have no concerns about your vision, it is still a good idea to have your eyes checked once every 2 years. Diseases such as glaucoma often don’t have any symptoms in their early stages, and are more easily managed if they are detected earlier.