Myopia (short-sightedness) is a term used to describe blurred distance vision caused by light focussing in front of the retina (the part of the eye which relays visual information to the brain) as a result of abnormal excessive eye growth. Although the vision of myopic individuals may be improved using spectacles or contact lenses, myopia causes other problems. Having myopia significantly increases lifetime risk of developing sight-threatening ocular conditions such as retinal detachment, myopic macula degeneration, cataract, and glaucoma (a largely symptomless disease which causes a loss of side vision due to increased internal eye pressure) [1]. The risk of ocular complications increases significantly with the level of myopia [1]. Myopia also places financial pressure on the individual, the National Health Service and other healthcare providers [2, 3], and has been shown to reduce quality of life for a mixture of psychological, cosmetic and practical reasons [4].
The number of people with myopia worldwide has increased sharply in recent years, reaching epidemic levels in East and South-East Asia, where up to 80 percent of the population are affected [5-7]. Myopia has also been become more common in the UK, USA and Europe, where between 20- 40% of the population are myopic [8-10]. Despite the increase in prevalence, the mechanism by which the eye is driven to grow excessively (become myopic) is not yet fully understood. We know that genetics has an important part to play as children with two myopic parents are 5-8x more likely to become myopic than those with one or no myopic parents [11-13]. However, this does not explain the sharp rise in the number of people with myopia in recent years, suggesting that other factors also play a role in myopia development [14, 15]. Research has shown that the eye grows in response to the visual environment, specifically myopia inducing blur [16-20]. Because myopia typically develops during the school years [15, 21], it has been associated with blur which may result from excessive close work (reading and using computers, tablets and smartphones). In myopia the eye is normally longer (compared with an emmetropic eye) and additionally, this altered shape profile may contribute to further progression of myopia [22,23]. The likelihood of an individual becoming myopic increases with the number of years spent in education and the level of educational achievement reached [24-26]. Research has also shown that children who become myopic tend to spend significantly less time outdoors than children without myopia [27-29]. It is suggested that spending upwards of 10-14 hours/week outdoors is protective against myopia [28-30]. It is believed that this could be due to a component of the light itself, or the reduction of myopia-inducing blur which occurs when viewing distant objects [31]. Myopia Control Options in response to research has shown that the rate of eye growth can be modified in response to the visual environment, several strategies have been investigated, with the aim of preventing myopia from developing or slowing its progression (myopia control or management). Various optical approaches to myopia control have been developed and evaluated over the past few decades. They are based around two different hypotheses, firstly the accommodative lag (small amount of blur we have when performing a near task) associated with myopia and secondly altering the peripheral defocus (amount of blur the eye receives in the periphery). Conventional single vision spectacles are thought to be ineffective for myopia control as they induce a relative peripheral hyperopic defocus (the focus falls behind the eye in the periphery), which is speculated to promote eye growth, see Figure 1. The modification of this peripheral defocus is the basis of orthokeratology, multifocal contact lenses and specially designed spectacle lenses.
The number of people with myopia worldwide has increased sharply in recent years, reaching epidemic levels in East and South-East Asia, where up to 80 percent of the population are affected [5-7]. Myopia has also been become more common in the UK, USA and Europe, where between 20- 40% of the population are myopic [8-10]. Despite the increase in prevalence, the mechanism by which the eye is driven to grow excessively (become myopic) is not yet fully understood. We know that genetics has an important part to play as children with two myopic parents are 5-8x more likely to become myopic than those with one or no myopic parents [11-13]. However, this does not explain the sharp rise in the number of people with myopia in recent years, suggesting that other factors also play a role in myopia development [14, 15]. Research has shown that the eye grows in response to the visual environment, specifically myopia inducing blur [16-20]. Because myopia typically develops during the school years [15, 21], it has been associated with blur which may result from excessive close work (reading and using computers, tablets and smartphones). In myopia the eye is normally longer (compared with an emmetropic eye) and additionally, this altered shape profile may contribute to further progression of myopia [22,23]. The likelihood of an individual becoming myopic increases with the number of years spent in education and the level of educational achievement reached [24-26]. Research has also shown that children who become myopic tend to spend significantly less time outdoors than children without myopia [27-29]. It is suggested that spending upwards of 10-14 hours/week outdoors is protective against myopia [28-30]. It is believed that this could be due to a component of the light itself, or the reduction of myopia-inducing blur which occurs when viewing distant objects [31]. Myopia Control Options in response to research has shown that the rate of eye growth can be modified in response to the visual environment, several strategies have been investigated, with the aim of preventing myopia from developing or slowing its progression (myopia control or management). Various optical approaches to myopia control have been developed and evaluated over the past few decades. They are based around two different hypotheses, firstly the accommodative lag (small amount of blur we have when performing a near task) associated with myopia and secondly altering the peripheral defocus (amount of blur the eye receives in the periphery). Conventional single vision spectacles are thought to be ineffective for myopia control as they induce a relative peripheral hyperopic defocus (the focus falls behind the eye in the periphery), which is speculated to promote eye growth, see Figure 1. The modification of this peripheral defocus is the basis of orthokeratology, multifocal contact lenses and specially designed spectacle lenses.
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Figure 1a) Demonstrates the image shell (red line) produced by conventional single vision spectacles, The image is focused at the fovea but peripheral hyperopic defocus is produced b) Demonstrates the image shell produced when both central and peripheral refraction is corrected. Which is the basis of myopia management treatment. |
Ineffective myopia control options:
• Undercorrection: This refers to the deliberate reduction of the power of spectacle or contact lenses prescribed to people with myopia who are at risk of becoming more myopic. Undercorrection of myopia with single vision spectacles was once thought to be an ideal strategy for myopia control as it reduced accommodative lag (the small blur we get when reading or performing another near task) which has been associated with myopia and its progression. This strategy has since been shown to be ineffective [32-34], and some research has shown that it causes accelerated eye growth (rather than slowing it down) [32, 33]. It also reduces the distance vision of the child, which could be detrimental to their education and safety.
• Rigid gas permeable (RGP) contact lenses: RGPs are known to provide the wearer with a sharper image than soft contact lenses. It was suggested that this clear image would prevent the eye from growing excessively. However, research has shown that these lenses are ineffective for myopia control [35, 36].
• Undercorrection: This refers to the deliberate reduction of the power of spectacle or contact lenses prescribed to people with myopia who are at risk of becoming more myopic. Undercorrection of myopia with single vision spectacles was once thought to be an ideal strategy for myopia control as it reduced accommodative lag (the small blur we get when reading or performing another near task) which has been associated with myopia and its progression. This strategy has since been shown to be ineffective [32-34], and some research has shown that it causes accelerated eye growth (rather than slowing it down) [32, 33]. It also reduces the distance vision of the child, which could be detrimental to their education and safety.
• Rigid gas permeable (RGP) contact lenses: RGPs are known to provide the wearer with a sharper image than soft contact lenses. It was suggested that this clear image would prevent the eye from growing excessively. However, research has shown that these lenses are ineffective for myopia control [35, 36].
Effective myopia control options:
• Bifocal, multifocal and gradient profile spectacle lenses: These lenses are thought to either reduce the level of myopia-inducing blur myopic people are exposed to when performing close work or by manipulation of the peripheral image shell (see figure 1) which is thought to drive eye growth. Research has shown that these lenses only offer a modest reduction in myopia progression [37-40].
• Multifocal and dual-focus contact lenses: As with multifocal spectacle lenses, these contact lenses both reduce the level of myopia-inducing blur myopic people are exposed to when performing close work and may impose a different type of blur peripherally (which is thought to slow down eye growth). Research has shown that these designs of contact lenses are significantly more effective than multifocal spectacles [41-45]. The results from a randomised controlled trial using dual focus contact lenses are such that use of these types of contact lenses could be considered for myopia management in children [44].
• Orthokeratology: Orthokeratology has been found to be an effective way to correct myopia through corneal reshaping with overnight wear of a rigid gas permeable lenses such that the wearer is contact lens and spectacle lens free during waking hours [46]. It has also been found to be a successful strategy in myopia control by causing central corneal flattening and paracentral corneal steepening which alters the image shell. As a consequence, the relative peripheral hyperopic defocus is reduced which is thought to remove the primary stimulus for axial elongation and subsequent myopia progression, see Figure 1. This strategy offers a significant reduction in myopia progression [47-55].
• Pharmaceutical intervention (atropine drops, pirenzepine gel, 7-MX tablets): Atropine has been known to prevent myopia development/progression since 1874. However, the mechanism by which it does this remains unknown. High doses of atropine (1.0%/0.5%) are initially most effective at preventing eye growth, but result in unwanted side effects such as blurred near vision and light sensitivity. Atropine 1.0% and 0.5% are known to cause accelerated eye growth after the individual stops taking them (rebound effect). Recent research has shown that low dose atropine (0.01%) is effective at reducing myopia progression with significantly fewer side-effects and rebound effects than 1.0% and 0.5% atropine. However the efficacy in slowing axial length is not confirmed. It is the increase in length of the eye that puts the eye at greater risk of future ocular disease [1]. Atropine 0.01% is not currently commercially available in the UK, but as research advances in this field, it may become available to suitably qualified optometrists in future. Pirenzepine gel was introduced as a possible alternative to atropine [56]. It was believed that it could have a similar anti-myopia effect with fewer side effects [57]. However, it is not licensed for ocular use, requires 2 doses/day (compared to 1 dose/day for atropine) [58], and it is less effective than low-dose atropine (which also causes minimal side effects) [59- 62]. 7-methylxanthine (7-mx) is a derivative of caffeine and has also been suggested to exhibit anti-myopia effects [63-65]. Clinical trials have shown that it has minimal anti-myopia effects [65].
• Time outdoors: There is a large body of epidemiological studies that point to the protective effect of time outdoors in myopia development and progression. A systematic review and meta-analysis found that the odds of myopia can be reduced by 2% per additional hour of time spent outdoors [66]. Additionally, it has been found that different amounts of light exposure slow axial length at different rates [67]. Findings from intervention studies on children that increased the amount of time they spend outdoors each day support the theory that increased time outdoors is influential in myopia development [68-71]. Despite the lack of uncertainty surrounding the mechanism of the protective effect of time outdoors it should be considered as an effective and straightforward strategy to reduce the risk of myopia development in children.
• Bifocal, multifocal and gradient profile spectacle lenses: These lenses are thought to either reduce the level of myopia-inducing blur myopic people are exposed to when performing close work or by manipulation of the peripheral image shell (see figure 1) which is thought to drive eye growth. Research has shown that these lenses only offer a modest reduction in myopia progression [37-40].
• Multifocal and dual-focus contact lenses: As with multifocal spectacle lenses, these contact lenses both reduce the level of myopia-inducing blur myopic people are exposed to when performing close work and may impose a different type of blur peripherally (which is thought to slow down eye growth). Research has shown that these designs of contact lenses are significantly more effective than multifocal spectacles [41-45]. The results from a randomised controlled trial using dual focus contact lenses are such that use of these types of contact lenses could be considered for myopia management in children [44].
• Orthokeratology: Orthokeratology has been found to be an effective way to correct myopia through corneal reshaping with overnight wear of a rigid gas permeable lenses such that the wearer is contact lens and spectacle lens free during waking hours [46]. It has also been found to be a successful strategy in myopia control by causing central corneal flattening and paracentral corneal steepening which alters the image shell. As a consequence, the relative peripheral hyperopic defocus is reduced which is thought to remove the primary stimulus for axial elongation and subsequent myopia progression, see Figure 1. This strategy offers a significant reduction in myopia progression [47-55].
• Pharmaceutical intervention (atropine drops, pirenzepine gel, 7-MX tablets): Atropine has been known to prevent myopia development/progression since 1874. However, the mechanism by which it does this remains unknown. High doses of atropine (1.0%/0.5%) are initially most effective at preventing eye growth, but result in unwanted side effects such as blurred near vision and light sensitivity. Atropine 1.0% and 0.5% are known to cause accelerated eye growth after the individual stops taking them (rebound effect). Recent research has shown that low dose atropine (0.01%) is effective at reducing myopia progression with significantly fewer side-effects and rebound effects than 1.0% and 0.5% atropine. However the efficacy in slowing axial length is not confirmed. It is the increase in length of the eye that puts the eye at greater risk of future ocular disease [1]. Atropine 0.01% is not currently commercially available in the UK, but as research advances in this field, it may become available to suitably qualified optometrists in future. Pirenzepine gel was introduced as a possible alternative to atropine [56]. It was believed that it could have a similar anti-myopia effect with fewer side effects [57]. However, it is not licensed for ocular use, requires 2 doses/day (compared to 1 dose/day for atropine) [58], and it is less effective than low-dose atropine (which also causes minimal side effects) [59- 62]. 7-methylxanthine (7-mx) is a derivative of caffeine and has also been suggested to exhibit anti-myopia effects [63-65]. Clinical trials have shown that it has minimal anti-myopia effects [65].
• Time outdoors: There is a large body of epidemiological studies that point to the protective effect of time outdoors in myopia development and progression. A systematic review and meta-analysis found that the odds of myopia can be reduced by 2% per additional hour of time spent outdoors [66]. Additionally, it has been found that different amounts of light exposure slow axial length at different rates [67]. Findings from intervention studies on children that increased the amount of time they spend outdoors each day support the theory that increased time outdoors is influential in myopia development [68-71]. Despite the lack of uncertainty surrounding the mechanism of the protective effect of time outdoors it should be considered as an effective and straightforward strategy to reduce the risk of myopia development in children.
Meta-analysis:
A recent meta-analysis (review) evaluated the relative effectiveness of all of the myopia control strategies [72]. The most effective myopia control interventions at preventing eye growth were atropine and pirenzepine [72]. However, current available concentrations are not suitable for myopia control (in terms of rebound and side-effects, as previously discussed) and low-dose atropine is not available in the UK at present nor shown to be effective in reducing axial elongation. Therefore the next most effective intervention strategies were orthokeratology therapy and multifocal contact lenses [72]. These optical intervention strategies are currently available to progressing myopes. On average the efficacy of these interventions is around 50% in terms of slowing myopia progression and axial length elongation. At this level of efficacy it is worth considering intervention.
Combined interventions
The mechanisms as to how these interventions play a role in slowing myopia progression is not fully understood and it may be that different pathways are involved with different intervention strategies. Therefore combining treatments with different mechanisms of action could also be more effective than monotherapies in slowing or preventing myopia progression. Researchers are investigating effects of low dose atropine combined with orthokeratology with some promising results and early results suggest that combined interventions may be more successful in slowing eye growth [73]. Given the limited data in this area at present and lack of access to low dose atropine in the UK we await longer term results for a clearer picture.
Final recommendations
No official guidelines currently exist for practitioners on myopia control. The International Myopia Institute (https://www.myopiainstitute.org/) are due to publish evidence based reports one of which will be on clinical guidelines. Research in the field of myopia control is ongoing and while we do not fully understand the mechanisms behind myopia development and progression we are at a stage where we can discuss myopia management in our clinical practice and have evidence based strategies available to actively manage myopia where applicable.
A recent meta-analysis (review) evaluated the relative effectiveness of all of the myopia control strategies [72]. The most effective myopia control interventions at preventing eye growth were atropine and pirenzepine [72]. However, current available concentrations are not suitable for myopia control (in terms of rebound and side-effects, as previously discussed) and low-dose atropine is not available in the UK at present nor shown to be effective in reducing axial elongation. Therefore the next most effective intervention strategies were orthokeratology therapy and multifocal contact lenses [72]. These optical intervention strategies are currently available to progressing myopes. On average the efficacy of these interventions is around 50% in terms of slowing myopia progression and axial length elongation. At this level of efficacy it is worth considering intervention.
Combined interventions
The mechanisms as to how these interventions play a role in slowing myopia progression is not fully understood and it may be that different pathways are involved with different intervention strategies. Therefore combining treatments with different mechanisms of action could also be more effective than monotherapies in slowing or preventing myopia progression. Researchers are investigating effects of low dose atropine combined with orthokeratology with some promising results and early results suggest that combined interventions may be more successful in slowing eye growth [73]. Given the limited data in this area at present and lack of access to low dose atropine in the UK we await longer term results for a clearer picture.
Final recommendations
No official guidelines currently exist for practitioners on myopia control. The International Myopia Institute (https://www.myopiainstitute.org/) are due to publish evidence based reports one of which will be on clinical guidelines. Research in the field of myopia control is ongoing and while we do not fully understand the mechanisms behind myopia development and progression we are at a stage where we can discuss myopia management in our clinical practice and have evidence based strategies available to actively manage myopia where applicable.
At Martin Reynolds Opticians we have been successfully helping myopes with orthokeratology from the age of 7 years and upwards.
The alternative to orthokeratology is MiSight 1 Day soft contact lenses, or the new MiYOSMART spectacle lens.
To book an appointment please call us on 01279 757767, or complete the form below for a call back.
The alternative to orthokeratology is MiSight 1 Day soft contact lenses, or the new MiYOSMART spectacle lens.
To book an appointment please call us on 01279 757767, or complete the form below for a call back.
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47. Cho, P., S.W. Cheung, and M. Edwards, The longitudinal orthokeratology research in children (LORIC) in Hong Kong: A pilot study on refractive changes and myopic control. Current Eye Research, 2005. 30(1): p. 71-80. 48. Cho, P. and S.-W. Cheung, Retardation of Myopia in Orthokeratology (ROMIO) Study: A 2- Year Randomized Clinical Trial. Investigative Ophthalmology & Visual Science, 2012. 53(11): p. 7077-7085. 49. Kakita, T., T. Hiraoka, and T. Oshika, Influence of overnight orthokeratology on axial elongation in childhood myopia. Invest Ophthalmol Vis Sci, 2011. 52(5): p. 2170-4. 50. Hiraoka, T., et al., Long-term effect of overnight orthokeratology on axial length elongation in childhood myopia: a 5-year follow-up study. Invest Ophthalmol Vis Sci, 2012. 53(7): p. 3913-9. 51. Santodomingo-Rubido, J., et al., Myopia Control with Orthokeratology Contact Lenses in Spain: Refractive and Biometric Changes. Investigative Ophthalmology & Visual Science, 2012. 53(8): p. 5060-5065. 52. Walline, J.J., L.A. Jones, and L.T. Sinnott, Corneal reshaping and myopia progression. British Journal of Ophthalmology, 2009. 93(9): p. 1181-1185. 53. Swarbrick, H.A., G. Wong, and D.J. O'Leary, Corneal response to orthokeratology. Optom Vis Sci, 1998. 75(11): p. 791-9. 54. Alharbi, A. and H.A. Swarbrick, The effects of overnight orthokeratology lens wear on corneal thickness. Invest Ophthalmol Vis Sci, 2003. 44(6): p. 2518-23. 55. Swarbrick, H.A., Orthokeratology (corneal refractive therapy): what is it and how does it work? Eye Contact Lens, 2004. 30(4): p. 181-5; discussion 205-6. 56. Stone, R.A., T. Lin, and A.M. Laties, Muscarinic antagonist effects on experimental chick myopia. Exp Eye Res, 1991. 52(6): p. 755-8. 57. Bartlett, J.D., et al., A tolerability study of pirenzepine ophthalmic gel in myopic children. J Ocul Pharmacol Ther, 2003. 19(3): p. 271-9. 58. Tabernero, J., et al., Effects of myopic spectacle correction and radial refractive gradient spectacles on peripheral refraction. Vision Res, 2009. 49(17): p. 2176-86. 59. Chia, A., Q.S. Lu, and D. Tan, Five-Year Clinical Trial on Atropine for the Treatment of Myopia 2: Myopia Control with Atropine 0.01% Eyedrops. Ophthalmology, 2016. 123(2): p. 391-9. 60. Siatkowski, R.M., et al., Safety and efficacy of 2% pirenzepine ophthalmic gel in children with myopia: a 1-year, multicenter, double-masked, placebo-controlled parallel study. Arch Ophthalmol, 2004. 122(11): p. 1667-74. 61. Siatkowski, R.M., et al., Two-year multicenter, randomized, double-masked, placebocontrolled, parallel safety and efficacy study of 2% pirenzepine ophthalmic gel in children with myopia. J AAPOS, 2008. 12(4): p. 332-9. 62 Tan, D.T., et al., One-year multicenter, double-masked, placebo-controlled, parallel safety and efficacy study of 2% pirenzepine ophthalmic gel in children with myopia. Ophthalmology, 2005. 112(1): p. 84-91. 63. Cui, D., et al., Effects of 7-methylxanthine on the sclera in form deprivation myopia in guinea pigs. Acta Ophthalmol, 2011. 89(4): p. 328-34. 64. Trier, K., et al., Biochemical and ultrastructural changes in rabbit sclera after treatment with 7-methylxanthine, theobromine, acetazolamide, or L-ornithine. Br J Ophthalmol, 1999. 83(12): p. 1370-5. 65. Trier, K., et al., Systemic 7-methylxanthine in retarding axial eye growth and myopia progression: a 36-month pilot study. J Ocul Biol Dis Infor, 2008. 1(2-4): p. 85-93. 66. Sherwin JC, et al. The Association between Time Spent Outdoors and Myopia in Children and Adolescents A Systematic Review and Meta-analysis. Ophthalmology. 2012. 119(10):2141- 51. 67. Read SA, et al. Light Exposure and Eye Growth in Childhood. Investigative Ophthalmology & Visual Science. 2015. 56(11):6779-87. 68. Zhou WJ, et al. Five-Year Progression of Refractive Errors and Incidence of Myopia in SchoolAged Children in Western China. Journal of Epidemiology. 2016. 26(7):386-95. 69. He MG, et al. Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China A Randomized Clinical Trial. Jama-Journal of the American Medical Association. 2015. 314(11):1142-8. 70. Jin JX et al. Effect of outdoor activity on myopia onset and progression in school-aged children in northeast china: the sujiatun eye care study. Bmc Ophthalmology. 2015;15:11. 71. Wu PC, et al. Outdoor Activity during Class Recess Reduces Myopia Onset and Progression in School Children. Ophthalmology. 2013;120(5):1080-5 72. Huang, J., et al., Efficacy Comparison of 16 Interventions for Myopia Control in Children: A Network Meta-analysis. Ophthalmology, 2016. 123(4): p. 697-708. 73. Kinoshita, N., et al. Additive effects of orthokeratology and atropine 0.01% ophthalmic solution in slowing axial elongation in children with myopia: first year results. Jpn J Ophthalmol. 2018. 62: 544
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