Myopia, or shortsightedness is a refractive disorder. Myopia occurs when the eye physically grows too long. When a light wave enters the eye, it is bent by the cornea as it makes its way through to land on the retina – the light-sensitive tissue in the back of the eye. If the eye is too long, the lens of the eye focuses the image in front of the retina instead of on top of it. People with myopia have good near vision but poor distance vision.
Causes of myopia
Myopia is most often inherited. However, the recent dramatic increase in the prevalence of myopia worldwide strongly suggests environmental causes, such as lack of time spent outdoors and a lot of close work like typing, reading, lab work or screen-time, may also significantly contribute to its development.
Prevalence of myopia in the United States has increased to about 40 per cent over the last 30 years. In East Asia, about 75 per cent of the population is myopic and, in some countries, myopia is as high as 90 per cent. Eyecare specialists are diagnosing myopia at younger and younger ages and the incidence of high myopia is increasing.
Myopia is of great concern for the World Health Organisation, eye care professionals, as well as parents. It is predicted that nearly half of the global population may be myopic by 2050.
Myopia leads to an increased risk of serious eye conditions such as myopic macular degeneration, retinal detachment, glaucoma, and cataracts that can lead to visual impairment or blindness. These eye diseases become more prevalent as the levels of myopia increase.
Optometrists work out how much focusing power your eye has. This is measured using dioptres – how strong a lens would have to be to give you focused vision. Myopia levels are based on how many dioptres your lens would need to be to correct your sight back to normal.
The higher the number the more short-sighted you are.
- Mild myopia can be defined as up to -3.00 dioptres (D). At this level of myopia, you normally are 100% dependent on glasses and or contact lenses, but you are not restricted in what glasses you can choose. Your spectacle lenses will be relatively thin and light.
- Moderate myopia has values of diopters from -3.00 to -6.00D. Usually, wearing the correct prescription glasses or contact lenses will mean your vision is fully functional.
- High myopia is usually myopia over -6.00D. In most cases, without glasses or contact lenses you will be legally blind.
The WHO believe that myopia will become a leading cause of permanent blindness worldwide.
The treatment for myopia includes spectacles, eye drops, contact lenses (orthokeratology or soft multifocal contact lenses), binocular vision training and exposure to light and the outdoors. Intervention before age 12 will have the biggest impact on reducing progression.
Myopia most often appears in children between the ages of eight and twelve and can worsen quite quickly through the teenage years. Between the ages of 20 and 40, there may be little or no change in vision. After 40, vision may begin deteriorating again.
Early, customised intervention myopia control plans have proven that the progression of myopia can be significantly slowed down or even stopped, and the subsequent risks from associated diseases also reduced.
It is important that children have regular eye examinations. Eye tests are even more critical if one or both parents are shortsighted.
Get an eye test
Early diagnosis of myopia can save your sight. To check your vision is 20/20, book an eye test by calling our Newmarket optometrist on 09 522 1283, Henderson Optometrists on 09 836 1731 or sending us an email via our contact page. What is myopia? We’d be happy to talk you through the causes and control programmes we can develop for you.