Myopia Control

How does myopia affect the eye?

In myopic eyes, light is focused in front of the retina rather than on it, causing blurry distance vision. Myopia tends to manifest in children (average age of onset being 8 years old) with younger age at diagnosis being associated with a higher risk of eye disease – as kids grow, so do their eyes.^4,5 Normally our eyes keep growing until the age of 14, after which it stabilises, however it has recently been discovered that 30% develop myopia after the age of 17!^1,4,5 In myopic eyes the normal growth pattern is interrupted and the eye continues to grow exponentially resulting in progressive myopia.¹

How bad are the risks, even just for low myopia?

Historically, myopia was considered a normal variation of the eye. Now there is a clear distinction between the two types of myopia:

• Myopia where the power of the eye is lower than –6D
• High myopia where the power of the eye is greater than –6D

Because myopia is progressive, over time the eye continues to grow longer, and the tissues at the back of the eye become stretched. Therefore, all levels of myopia increase the chance of myopic eye disease such as retinal detachment, cataracts, glaucoma and other retinal degenerations.² This escalates as the level of myopia increases and the tissue is stretched further, especially once the length of the eye exceeds 26.5mm (‘pathological myopia’).⁵ 1 in 4 people with eyes longer than 26mm are at risk of permanent vision loss, compared to 1 in 25 with eyes smaller than 26mm.³ Even if the eye is under 26.5mm long, the risk of glaucoma with myopia is similar to the risk of stroke when smoking over 20 cigarettes a day, and retinal detachments are a frequent occurrence.^1,4 Reducing the amount of myopia your child develops keeps the risk as low as possible. It also reduces the thickness of glasses your child will require, as well as their reliance on them.

What are the risk factors for developing myopia?

While a family history of myopia contributes to the development of myopia, other factors are involved.⁷ Studies have shown that the more time a child spends on activities up close (including on electronic devices) and the less time spent outdoors, the more likely they are to become short-sighted.⁷ This is thought to partly explain why the number of children developing myopia across the globe is on the rise. Additionally, those who become myopic at a younger age are at greater risk for developing a higher degree myopia.⁷ Difficulty with the co-ordination of both eyes (binocular vision disorders) have also been linked to progression of myopia.⁷

How can myopia be controlled?

Unfortunately, standard glasses and contact lenses are ineffective in slowing the progression of short-sightedness.⁷ However, there are other treatment options that can control growth. At Innovative Eye Care, we take a proactive role in developing a custom treatment regime based on your child’s lifestyle, age and prescription. The main interventions are listed below, as well as basic changes including at least 2 hours outdoors each day and limiting near activities (including electronic devices) to 45 minutes at a time.⁷

Innovative Eye Care’s myopia control treatment options

Orthokeratology

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 reversibly and temporarily reshapes the cornea (front surface of the eye) while you sleep, providing clear vision the next day without the need for spectacles or contact lens wear during the day.

As well as being convenient, ortho-K actually slows and in some cases stops myopia progression.^8,9,10 Ortho-K has been proven to slow myopia progression by 32-100%, depending on the study, or an average 50% reduction.^8,9,10 Results in our practice and from other myopia control practices in Australasia show complete halting of myopia progression in some patients.

Atropine eye drops

Atropine is a prescription eye drop that primarily works by relaxing specialised muscles in the eye. It’s been used safely over the decades for a range of eye conditions, including for myopia control. It’s currently thought that the atropine molecule also acts on receptors at the back of the eye that initiate eye growth.¹⁰ Evidence has shown that the effect on myopia control is a dose-dependent relationship – the higher the concentration of atropine, the greater the effect on slowing down axial length growth.^5,10,11 Side effects like blurry vision and glare are unlikely to occur at the concentrations atropine is prescribed, but can be an issue at higher concentrations. These side effects are reversible upon cessation and have not been shown to cause any long term changes.¹¹ Currently, atropine used for myopia control is only found at compounding pharmacies as they are not readily available at concentrations below 0.5%. They need to be instilled nightly to prevent progression.

Multifocal contact lenses

Multifocal soft contact lenses are typically used by people over 45 to improve their near vision. The word ‘multifocal’ comes from ‘multi’ meaning many and ‘focal’ relating to focus, where multifocal contact lenses can focus light from multiple distances at once, unlike single vision lenses. The retina responds to this pattern of focus by signalling for the slowing of eye growth.¹⁰ This refocussing occurs in ortho-K as well, and this optical property is thought to be responsible for slowing eye growth. Multifocal soft contact lenses have been found to be slightly less effective than ortho-K with only a 40% reduction in myopia progression.¹⁰

Spectacle lenses

The latest research in myopia control has found that a new spectacle lens design known as DIMS (defocus incorporated multiple segments) is also effective in slowing the growth of the eyeball using similar optics as custom contact lenses.¹² DIMS lenses, also known as Hoya MiyoSmart, slow progression by a promising 60% on average, offering children a non-invasive myopia control option.¹² Progressive spectacle lenses may also be used to control myopia depending on your child’s binocular vision status, which is tested during the eye examination.¹³

How do we know it’s working?

Success of a chosen treatment is based on how much myopia progresses throughout. However, not all methods of measuring myopia are created equal. While all optometry practices can quantify whether your child’s prescription has changed with subjective refraction, this doesn’t reliably tell us how much the eye has grown. Since preventing eye growth is the sole reason for myopia control, subjective refraction alone is a poor marker for success. We use the following techniques to accurately assess myopia:

• Ocular biometry: Directly measures the axial length of the eye at every visit, down to the micron (1/1,000^th of a millimetre)⁷
• Corneal topography and tomography: Maps the shape of the front of the eye to determine its optical power and to fit custom contact lenses like ortho-K.
• Objective refraction: Measures myopia when focussing is relaxed, giving a truer refractive reading than when measured subjectively.⁷

The most important of these metrics is ocular biometry measuring axial length.It has the least variability and directly relates to the myopic disease process.⁷ We can compare your child’s axial length against what is normal for a child of their age, and whether they are at a greater risk of disease.

Rather than rely on subjective refraction alone, these methods combined give us the complete picture; we know exactly what components of the eye are contributing to myopia. We can then better tailor myopia control strategies for your child and closely monitor for any progression throughout.

References

1. Brien Holden Vision Institute & World Health Organisation. (2016). “The Impact of Myopia and High Myopia.” Report of the Joint World Health Organisation: Brien Holden Institute Global Scientific Meeting on Myopia.
2. Flitcroft, D. I. (2012). “The complex interactions of retinal, optical and environmental factors in myopiaaetiology.”Progress in Retinal and Eye Research31(6): 622-660.
3. Willem, J. et al. (2016) ‘Association of Axial Length with Risk of Uncorrectable Visual Impairment for Europeans with Myopia’. JAMA Ophthalmol. 134(12): 1355-1363.
4. Goldschmidt, E. Jacobsen, N. (2013). ‘Genetic and environmental effects on myopia development and progression’. Cambridge Ophthalmological Symposium. 28(1): 126-133.
5. Flitcroft, D. I., et al. (2019). “IMI-Defining and Classifying Myopia: A Proposed Set of Standards for Clinical and Epidemiologic Studies.”InvestOphthalmolVis Sci.60(3)
6. Chen-Wei, P. Ramamurthy, D. Seang-Mei, S. (2011). ‘Worldwide prevalence and risk factors for myopia’. Opthalmic and Physiological Optics. 32(1).
7. Gifford, K. et al. (2019). “IMI - Clinical Management Guidelines Report”. InvestOphthalVis Sci. 60(3)
8. Na, M. Yoo, A. (2018). “The effect of orthokeratology on axial length elongation in children with myopia: Contralateral comparison study”. Jpn J Ophthalmol. 62(3): 327-334.
9. Hiraoka, T. et al. (2012). “Long-term effect of overnight orthokeratology on axial length elongation in childhood myopia: a 5-year follow-up study”. Invest Ophthalmol Vis Sci. 53(7): 3913-3919.
10. Wildsoet, C. et al. (2019). “IMI- Interventions for Controlling Myopia Onset and Progression Report”. InvestOphthalmolVis Sci. 60(3).
11. Bullimore, M. A, Richdale, K. (2020). “Myopia Control 2020: Where are we and where are we heading?” Ophthalmic Physiol Opt. 40(3): 254-270.
12. Lam, CSY, et al. “Defocus Incorporated Multiple Segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomised clinical trial.” Br J Ophthalmol 104(3):363-368.
13. Cheng, D. et al. (2014). “Effect of bifocal and prismatic bifocal spectacles on myopia progression in children: three-year results of a randomised clinical trial” JAMA Ophthalmol. 132:258-293.