Myopia, or short-sightedness, is a focusing disorder of the eyes that causes blurring of distance vision. A characteristic of myopia is that it typically worsens during the childhood and teenage years, before stabilising at 20-something years of age. While low levels of myopia are not concerning from an eye health point of view, moderate to high myopia is associated with increased risk of serious eye conditions such as retinal detachment, glaucoma, and myopic maculopathy.
We now have good evidence-based strategies which have been shown to slow the progression of myopia. These should be considered if a young person appears to be developing progressive myopia, to reduce the risk of myopia-related pathology.
What is Myopia?
Myopia is the result of an imbalance between the focusing power of the eye and the length of the eyeball. A properly focused eye will focus light on the retina, at the back of the eye. A myopic eye is too long for the focusing power of the eye, and light will focus in front of the retina, causing blurred distance vision.
The prevalence of myopia is increasing at an alarming rate world-wide. Globally it is estimated that about 1.5 billion people, or 22% of the world's population, are myopic. The prevalence is greater in industrial societies and cities than in rural areas.
In the United States, the prevalence of myopia increased from 25% in 1972 to 42% in 2004, with the incidence of high myopia (over -5.00) having increased eightfold. One study predicts that 65% of the world's population will be myopic by 2050, with 20% of those predicted to be highly myopic.
The high and increasing prevalence of myopia, combined with the potentially serious consequences of the condition, make myopia a significant public health concern. The key to avoiding the majority of serious myopia-related pathology is to reduce the levels of high myopia.
Studies suggest that slowing the rate of myopia progression by 33% would result in a 73% decrease in the number of highly myopic eyes. This sort of slowing is achievable using current methods of myopia control.
What Causes Myopia?
There is no simple answer to this. We know that a number of factors are associated with increased risk of myopia. These include:
- Genetics - having 2 myopic parents increases the risk of myopia by about 5x
- Near Work - there is good evidence that large amounts of close work tend to be associated with myopia development
- Lack of Outdoor Time - recent studies suggest that natural sunlight and time outdoors reduces the risk of developing myopia
- Asian Ethnicity - the rate of myopia, and particularly high myopia, seems to be higher among East Asians
- Intelligence - in good news, there is a positive correlation between myopia and intelligence
Much recent research suggests that a major stimulus to myopia is hyperopic (long-sighted) blur on the peripheral retina. This discovery has been valuable in developing strategies to slow myopia progression.
The implication is that specially designed lenses that deliberately cause myopic defocus in the peripheral retina may reduce the stimulus for the eye to grow further, thus slowing or preventing an increase in myopia. This is the scientific basis for using MiSight soft multifocal contact lenses, Stellest and MiYOSMART spectacle lenses, and orthokeratology to control myopia.
Myopia Control Strategies
It is important to understand that myopia control techniques cannot reverse myopia. The aim is to slow the rate of myopia progression, or ideally stop progression altogether. It is also important to understand that the effectiveness of myopia control strategies will vary between individuals.
The first line of defence against myopia is lifestyle modification. This includes getting kids to spends a decent amount of time outside and off screens, and to take regular breaks from close work. Although this is always a good start, it may not be enough. The heavy-hitting myopia control options are outlined below:
Spectacle Lenses for Myopia Control
There have been exciting developments in spectacle lens technology recently, with two new lens designs that have been shown to slow myopia progression. The Stellest lens from Essilor, and the MiYOSMART lens from Hoya are proving to be effective at slowing progression of myopia.
These innovative technologies utilise a treatment zone of miniature lenslets to create myopic defocus on the peripheral retina. Studies are showing a 60% slowing of myopic progression, compared with single vision spectacle lenses. This is much better than previous attempts at myopia control using spectacles, and about equivalent to MiSight contact lenses or orthokeratology.
The Stellest and Miyosmart lenses are a great myopia control option for children that are not ready, or not interested, in contact lens wear.
Contact Lenses for Myopia Control
Orthokeratology, also known as Ortho-K and Corneal Reshaping Therapy (CRT), involves using specially-designed hard lenses which are worn overnight in order to reshape the cornea. Ortho-K reduces myopia progression by creating peripheral myopic defocus, and is an effective means of myopia control.
At Cassidy Eyecare, we utilise scan data from our corneal topographer to create customised ortho-K lenses. This therapy is only available in our New Lynn office.
Further information on our orthokeratology service can be found here.
MiSight Soft 1 Day Myopia Control Contact Lenses
For the past few years we have been utilising the MiSight Daily Disposable contact lens to control myopia in children and teenagers. We have been very impressed with the results - clinical studies show a reduction in myopia progression of 59%, and our personal experience with this lens is similar. It definitely works.
MiSight contact lenses work on the principle of creating myopic defocus in the peripheral retina, which sends a signal to the eye to stop growing. These contact lenses are a single-use disposable contact lens, so they are comfortable, easy to look after, and very safe.
At Cassidy Eyecare, we have been very impressed with the effectiveness of MiSight as a myopia control strategy, and highly recommend this product for young myopes capable of handling contact lenses.
Eye Drops for Myopia Control
Atropine Eye Drop Therapy
Atropine is a natural chemical derived from Belladonna, and has been known since ancient times. It has powerful effects on the eye, which include pupillary dilation and paralysis of eye focusing. Although a number of studies over several years have shown that atropine may slow progression of myopia, the side effects made it impractical. However, recent studies have shown that even very dilute atropine is effective in slowing myopia progression.
Dilute atropine eye drops appear to slow myopia progression by about 50%, although the mechanism by which it achieves this is unclear. Atropine eye drops for myopia control are not available as a pre-packaged medication, and need to be made to order by a compounding pharmacy. The dosage for atropine is one drop at night in each eye. They can be used in conjunction with MiSight 1 Day contact lenses, or Stellest/MiYOSMART spectacle lenses.
The drawback with atropine is that, while it may work to slow myopia progression, it does not provide vision correction. Spectacles or contact lenses are still needed to provide clear vision. For this reason we tend to utilise atropine as a back-up or additional treatment, rather than as a first-choice treatment.
We recommend My Kids Vision as a good source of information for parents wanting to know more about myopia and myopia control.