Are Glasses an Outdated Way of Correcting Your Child’s Eyesight?
Your child has been told by the optometrist that he or she needs glasses. To see better at school and in the far distance. It seems straightforward enough. Glasses will fix the problem, right?
Now imagine this:
You go to see your dentist about a toothache. He finds a decaying tooth and then prescribes you with painkillers to relieve the pain. You feel better for a while but the toothache comes back and is getting worse. So you go back to the dentist, and he prescribes a stronger painkiller. Meanwhile, your tooth continues to decay.
In a way, that’s how optometrists and opticians have traditionally managed childhood short-sightedness, or myopia. By prescribing a pair of glasses.
Glasses help to mask the symptoms of myopia—by refocusing the light entering the eye and reducing blur—but the underlying progressive condition, abnormal eye growth, is left untreated. Then, as the myopia increases and the blurred vision returns, stronger and thicker glasses are prescribed. And repeat.
Spectacle lenses for short-sightedness are believed to have been invented in the 16th century, when it was discovered that concave lenses could improve far-distance sight. In more recent times, glasses have become more widely accepted, more popular, fashionable even. Lens manufacturing processes have also advanced. But the fundamental principles of the optics behind single-vision lenses have essentially remained the same for years.
With myopia, objects in the far distance are imaged in front of the retina (the ‘film’ that allows us to see) as the eye is too long for its focusing power. A concave-shaped, minus-powered spectacle lens refocuses this image back towards the retina, restoring clear vision. But the back of the eye isn’t a flat surface like film in a camera.
When a corrective lens is placed in front of the eye, straight-ahead vision is clear as the image falls directly in the central area of the retina, the fovea, but peripheral vision is actually blurred, as light is focused behind the plane of the retina, due to the curvature of the eyeball. In scientific terms this is called ‘peripheral hyperopic defocus’.
In recent years, it has emerged that one of the driving forces behind the elongation of the eye with myopia may be caused by signals originating from the peripheral areas of the retina, and that peripheral hyperopic defocus plays a role in influencing the eye to grow longer. In addition, it has been shown that correcting myopia with conventional single-vision spectacle lenses increases hyperopic defocus, especially in children with moderate myopia.
So glasses that are prescribed to correct vision may in fact, inadvertently, be contributing to the worsening of the condition they were made to treat.
When I was a boy and got my first pair of glasses at age 8, there was no knowledge that myopia could be treated with anything other than glasses. As I grew up, my eyes worsened with each passing year until they eventually stabilised on their own in my 20s—leaving me with me severely stretched, 28mm-long eyeballs, high myopia of -8.00 and significant risks of developing retinal disease in my lifetime. Without my glasses, I can see only just past the tip of my nose.
In all areas of medicine and health sciences there are endless pursuits in advancing knowledge through research. With that we gain greater and deeper understanding of new ways to best treat health conditions. Think of all the medical conditions that, once upon a time, were considered ‘untreatable’.
Myopia is now a treatable condition. There is clinical evidence aplenty that we can slow down the progression of short-sightedness in children and adolescents, with methods aimed at arresting the abnormal eye growth.
The window of opportunity to do something about keeping your child’s level of myopia to a low level is limited. It may not seem like a big deal when their first pair of glasses are quite mild, at say -1.00. But a year later it may have doubled to -2.00, then -3.50, and so on, down a slippery slope towards high myopia and higher lifelong risk of eye diseases.
This kind of alarming prescription increase is not uncommon for children who are simply wearing single-vision glasses. We, as optometrists, see this scenario in our clinics all too often. It doesn’t take long for myopia to progress during a child’s growth spurt years.
And the younger the child when first diagnosed with myopia, the more potential and time there is for the eye to grow longer. The average adult human eye is around 23.3mm long, from the front surface to the retina. For every millimetre of eye growth, and every dioptre of prescription increase, the risk of eye disease increases.
The stretching and elongation of the eyeball causes a thinning of the eye’s inner layers and multiply the life-long risks of developing glaucoma, myopic macular degeneration and retinal detachment — conditions that can lead to permanent vision impairment. Going blind is not something that anyone wants to think about, at any age.
Eye growth that has already occurred cannot be reversed; it is permanent. It is a common misconception that laser surgery will fix myopia — laser refractive surgery improves vision but eliminating blur, just as glasses do but in a permanent way, but it does not reduce the eye disease risks of an already-stretched eyeball.
There are new, exciting developments for spectacle lenses in the pipeline to address the deficiencies in the optics of regular single-vision lenses for children with myopia.
Developed in collaboration with the Hong Kong Polytechnic University, Japanese lens manufacturer HOYA is set to launch the innovative MyoSmart lens later this year in Hong Kong and China, with expected global release in 2019–2020.
The MyoSmart lens features Defocus Incorporated Multiple Segments (DIMS) technology. What this means is the lens has a regular central vision zone to correct vision, surrounded by hundreds of ‘micro-lenses’ in the mid-periphery to create constant myopic defocus for the wearer, thus reducing the peripheral hyperopic defocus that contributes to myopia progression.
While attempts to create peripheral myopic defocus in a spectacle lens is not entirely new—the Zeiss MyoVision lens with ‘peripheral vision management’ has been available, primarily in Asia, since 2011—this new DIMS lens is said to maintain its peripheral defocus effects even as the eye moves behind the spectacle lens, something that was a shortcoming with previous lens designs.
Until new generations of spectacle lenses like the MyoSmart become readily available, the best ways to control the abnormal elongation of the eye and reduce your child’s myopia progression is not with glasses but with special types of contact lenses: Orthokeratology (Ortho-K) and multifocal soft contact lenses.
Both of these types of contact lenses provide clear central vision while simultaneous modifying the defocus in the peripheral retina to reduce the stimulus for eye growth. With Ortho-K, this effect is moulded onto the surface of the eye with special corneal-reshaping lenses worn during sleep, while multifocal soft contact lenses are effective as the lens is worn during daytime.
You may ask, is my child suitable for contact lenses? Are contact lenses actually safe for kids?
Most children are suitable for contact lens wear and experienced practitioners can safely fit contact lenses for children as young as 5–6 years of age. And although contact lenses seem like a riskier option than wearing glasses, research has shown that contact lenses are indeed safe for children and can even improve their quality of life and self-esteem. Ortho-K night-time lenses, in particular, are worn under parental supervision in the comfort and safety of home.
What if I still prefer my child to wear glasses?
If you decide that your child is not yet ready for contact lenses, there are glasses options other than single-vision lenses that have shown some effect in slowing myopia progression, albeit with less much efficacy than the above contact lens options. Multifocal and bifocal spectacle lenses can reduce near focusing effort when a child reads up-close with their glasses on, which for some children can be beneficial.
Alternatively, your optometrist may be able to prescribe a pharmacological treatment called atropine to help slow progression. Atropine, in a low-dose compounded eye drop form, most commonly 0.01%, has shown effective myopia control in research after a 5-year period, while maintaining a good safety profile without significant side effects or adverse reactions.
In clinical practice, the only time I am comfortable with prescribing a set of single-vision glasses for a myopic child with a high risk of progression is if the child is also concurrently on atropine treatment.
The expectation you should have from your optometrist is that your child’s blurred vision from myopia is viewed as a potentially progressive eye health condition rather than just a simple vision problem.
That means an explanation of the likely prognosis of this condition based on an evaluation of the risk factors identified, and a discussion of the myopia management options available to treat it to prevent future vision loss. Your child should be monitored closely so that appropriate treatment can be initiated at the earliest signs of progression.
To be simply prescribed with a regular set of single-vision glasses is merely putting a band-aid on a problem that is very likely to worsen. In this day and age, with what we now know about myopia, your child’s eyes deserve better than an outdated approach with technology from last century.
If your child has been diagnosed with myopia and prescribed glasses for the first time, it’s time to think—is there a better way to treat my child’s eye condition?
