Myopia, or shortsightedness, is increasing around the world, with many calling it an epidemic. A more urbanised, more educated and more screen based society seem to be the primary drivers for the increase in short sighted eyes. The adaptations of the eye to focus at nearer objects not only reduces distance vision and requiring glasses or contact lenses, but it also increases the risk of irreversible eye disease. If you would like to know more about the treatment options we offer here at Innovative Eye Care to slow the progression of myopia, book an appointment or find out more by giving our friendly staff a call.
For most people short-sightedness evokes the harmless image of a school-aged child using glasses to see the television and school board clearly. But the real change that progressive myopia represents is a lengthening of the eyeball which increases the risk of eye disease. And these are changes are happening at a rapid rate, with prevalence predicted to reach half the world's population by 2050.
The prevalence varies with some groups of people seem to be developing more myopia than others: higher educated, more densely populated, asian race.
Myopia causes with the lengthening of the eye and this lengthening happens as a result of stretching of the tissue of the eye, not eye growth. Myopia can start to develop at any age but the younger the start, the more aggressive the progression of myopia and eye lengthening tends to be. High myopes will be highly dependent on more expensive, heavy, high-powered glasses or contact lenses for any visual tasks. They may also have to keep updating their prescription lenses each year as their eye becomes more shortsighted.
Historically, low myopia was considered as normal variation of the eye, a harmless adaptation of the eye to increased near vision demands, and a distinction was made between:
For this model to be valid, there should be a cutoff under which the degree of myopia has an acceptably low level of risk for eye disease, but this does not appear to happen. Any magnitude of myopia carries significant increased risk of permanent, uncorrectable vision loss compared to a non-myopic eye.
How bad are the risks, even just for low myopia?
“Myopia in the so-called ‘physiological range’ represents a major risk factor for ocular disease that is comparable with the risks associated with hypertension for cardiovascular disease or with the risks of stroke from smoking more than 20 cigarettes per day.“ (Flitcroft)
“For retinal detachment and myopic maculopathy, myopia carries a risk far in excess of any identified population risk factor for cardiovascular disease” (Flitcroft)
These conditions are far from rare: myopia maculopathy, a progressive condition causing breakdown of retinal cells, is the forth most common cause of visual impairment in the UK, ahead of diabetic eye disease.
An important concept to re-iterate is that while the risks of eye disease later in life are present for any degree of myopia, the higher the amount of myopia, the higher the risk. An Australian study showed myopes of above -5D had a myopic retinopathy prevalence 60 times that of lower myopes. The lifetime chance of a retinal detachment in patients with more than -5D of myopia is around 5% compared to 0.3% for the general population. If we can stop the progression of myopia into these high levels then a significant amount of blindness can be prevented. Studies suggest that even a modest reduction in the rate of myopia of 33 % could produce a 73 % reduction in myopia above 5.00 D.
The personal case of one of our previous optometrists, Alex Petty, highlights why myopia control is so important. Alex developed myopia at the age of 9. This progressed throughout his teenage years, eventually stabilising at a high -7.50D in each eye. As a result, Alex suffered two retinal detachments in his left eye in 2009 and another in 2014 in his right. Fortunately through timely surgery, these were able to be repaired with only slight vision loss. If Alex had access to myopia control treatments when he was a teenager, it is unlikely his prescription would have worsened as quickly and these ocular emergencies might have been prevented. His experience has fueled a passion to treat young people with myopia and prevent eye disease later in their lives.
CAPTION: The appearance of Alex's eye after his retinal detachment surgery (left) and some of the retinal scar left after surgery in Alex's eye (right). This peripheral part of his vision is now permanently blind.
Prescribing standard spectacle lenses or contact lenses will do nothing to halt the lengthening of the eye. As a result, the patient will require frequent spectacle lens updates and will be put at risk of sight-threatening disease in the future. Unfortunately, the lengthening of the eye which causes myopia cannot be reversed, making it critical to control myopia sooner rather than later.
From Huang et al 2016
The good news is, there is convincing evidence that certain treatments can slow and even halt the progression of myopia. Orthokeratology and topically administered atropine drops have been shown to be the two most effective tools currently available to control myopia. These options have different pros and cons, so it is necessary to determine an appropriate treatment plan with your optometrist. Other treatment options do exist, though they do not show the same level of myopia control.
CAPTION: Myopia control can slow progression by 50% and lower the risk of blindness
Orthokeratology (or Ortho-K) is a type of contact lens wear which has been practiced at Innovative Eye Care for many years. Ortho-K involves wearing a custom-designed contact lens overnight which reshapes the surface of the eye, giving clear vision the next day without the lenses. As well as being convenient for the patient, the treatment actually slows and in some cases stops myopia progression. When myopic eyes are corrected with conventional spectacles and contact lenses, light entering the eye centrally will focus at the retina; however, light entering off-centre will focus behind the retina. This is thought to stimulate lengthening at the back of the eye as the retina tries to reach the focal point behind the eye, worsening the condition. Ortho-K lenses can slow this growth by changing the shape of the eye surface, allowing central light to focus accurately at the retina and off-centre light to focus in front of the retina. The retina will no longer 'attempt' to elongate.
Research has now shown a range of 32%-100% slowing of myopia progression depending on the study. Most reports suggest an average of a 50% reduction in the rate of myopia progression with ortho-K contact lens wear. Results in our practice and from other myopia control practices in Australasia show complete halting of myopia progression in some patients.
Atropine drops have been used for many years to control myopia; however, until recently they have been prescribed at a normal concentration of 0.5% - 1%. Atropine at this concentration causes loss of focusing in young children for near tasks and dilates the pupil leading to light sensitivity. For young patients that show aggressive myopia progression we will still recommend 1% atropine in order to best control their myopia progression. These drops are used in conjunction with tinted transitions progressive lenses to give protection from bright light and the ability to see for reading tasks.
Studies over the last decade have found that much lower concentrations of atropine, such as 0.02%, have a comparable reduction in myopia progression, without any noticeable effect on pupil size or near-focusing. For example the ATOM2 study showed the myopia control effect of 75% reduction for the 1%, 0.5% and 0.1% concentrations and 65% reduction with 0.01%. Studies have told us that 0.02% is the highest concentration of atropine that shows no significant change to near focusing or pupil size in children, and has no reported allergic side effects.
It was initially thought that as atropine drops paralyse the focusing muscles of the eye, this was the reason for the myopia control. Our understanding now suggests that the atropine molecule affects a receptor in the choroid or sclera of the eye (the vascular and structural layers of the eyeball), signalling to the eye not to continue to elongate. This mechanism is still being studied.
Atropine drops need to be instilled nightly and can be combined with Ortho-K therapy to maximise the myopia control effect. Visual and general side-effects are highly unlikely at 0.02%. Atropine drops will need to be specially formulated at a compounding pharmacy as they are not readily available at concentrations below 0.5%.
Certain types of soft contact lenses have been used and developed to control myopia. Multifocal soft contact lenses are typically used by people over 40 yo to improve their near vision. These have a similar peripheral area of steepening on the lens like Ortho-K, although at a lower level (maximum +3D, whereas the ortho-K example above shows a +8D difference!). As a result, when these soft contacts have been used by young patients, studies have only reported a modest range decreased progression of 29-45% . Specialised soft contact lenses called MiSight (Coopervision) have been designed by a research team in New Zealand specifically with myopia control in mind, and have been TGA approved for the indication of controlling myopia progression. These lenses show a 40% reduction in myopia progression. If Ortho-K lenses are not suitable, these soft contact lenses may be discussed by your optometrist as an alternative option, and may be used in conjunction with atropine drops.
As mentioned previously, regular spectacles offer no myopia control benefit. In some individuals that are myopic and progressing and that show a near esophoria (tendency of the eyes to turn in more than required when reading) or an accomodative lag (eyes do not focus close enough when reading) then progressive addition spectacles lenses may offer some myopia control benefit. The near conditions mentioned above are tested by your optometrist during their appointments. Studies are varied but suggest a reduction of myopia progression in the range of 12-55% with these lenses.
Myovision spectacle lenses are specially designed for controlling myopia but studies suggest they only slow progression by 0-30%. As a result they are infrequently used.
Apart from active interventions, there is also sufficient evidence for the modification of lifestyle factors of time spent on near work and time spent outdoors. Less near work, or more regular breaks plus more time outdoors in natural light are protective against eye length growth.
There is an excellent website by Richard Anderson (myopiaprevention.org) which explains in detail all aspects of myopia control with the relevant research included.
Axial eye length is the best metric of risk and progression for myopia. It has the with the least variability and directly relates to the disease processes that myopia can create. If you are concerned about your child’s eyes becoming progressively short-sighted, please contact our friendly team to arrange a consultation with one of our optometrists to discuss their myopia and what may be done to arrest this progression.
Brien Holden Vision Institute. The Impact of Myopia & High Myopia. 2015, NSW: World Health Organisation.
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