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.
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.
There is no simple answer to this. We know that a number of factors are associated with increased risk of myopia. These include:
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 impetus 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 and orthokeratology to control myopia.
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:
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, 2 large-scale studies have shown that even very dilute atropine is effective in slowing myopia progression. Atropine at a concentration of 0.01% was shown to be clinically equivalent to stronger dosages, but with minimal side effects.
Atropine 0.01% eye drops appear to slow myopia progression by about 50%, although the mechanism by which it achieves this is unclear. Atropine 0.01% eye drops are not available as a pre-packaged medication, and need to be made to order by a compounding pharmacy. The dosage for atropine 0.01% drops is one drop at night in each eye. They can be used in conjunction with MiSight 1 Day contact lenses if desired.
At Cassidy Eyecare, we are excited to be one of a limited number of optometry practices to have access to the MiSight Daily Disposable lens, designed specifically for myopia control. MiSight uses a unique design to create peripheral myopic defocus, while allowing clear vision for the central retina. Clinical evaluation studies are showing a 59% reduction in myopia progression using a MiSight lens compared with regular soft disposable contact lenses. Because MiSight lenses are designed for daily replacement, they are a very easy, comfortable and safe way to wear contact lenses.
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. Studies show about a 40% reduction in myopic progression, although anecdotally higher rates are reported.
We do not offer orthokeratology at Cassidy Eyecare, but can recommend colleagues who are experienced in this form of myopia control.
Studies have shown special spectacle lenses to be of value in myopia control when myopia is associated with some eye co-ordination problems. Evidence also shows that it is important for the most up-to-date prescription to be worn - under-correction has been shown to increase the rate of myopia progression.
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