Sudanese Journal of Ophthalmology

REVIEW ARTICLE
Year
: 2019  |  Volume : 11  |  Issue : 1  |  Page : 1--7

Strategies in myopia prevention and management


Yazan Sultan Gammoh 
 Department of Optometry, Faculty of Allied Medical Sciences, Al-Ahliyya Amman University, Amman, Jordan

Correspondence Address:
Dr Yazan Sultan Gammoh
Department of Optometry, Faculty of Allied Medical Sciences, Al-Ahliyya Amman University, P.O. Box 121, Amman 19328
Jordan

Abstract

It has been estimated that more than half of the population residing in the Eastern Mediterranean region (EMR) will have myopia by 2050. With recent evidence from the EMR revealing that myopia is becoming more prevalent in children and presenting at a younger age than seen before, it is of importance to investigate the strategies employed in myopia control. Various intervention strategies have been investigated in the last few years including optical, pharmacological, and environmental modification methods. Spectacle-based strategies including use of bifocal lenses and progressive addition lenses (PALs) have been shown to be the least successful in reducing the progression of myopia. However, the use of such lenses provides better myopia control than prescribing single-vision lenses or under-correcting, which may increase myopia progression. Since many practitioners in the region are only allowed to prescribe and fit spectacles, the use of bifocals and PALs should not be neglected. Multifocal contact lenses and orthokeratology have proven to be successful clinically in the management of myopia. However, cost and limited availability of these lenses in the region are barriers for the use of these lenses by EMR practitioners. Use of atropine has been shown to be effective in controlling myopia progression. With the limited scope of practice regarding the use of diagnostic drugs by optometrists, there is need for advocating to allow optometrists to use ocular diagnostics such as atropine. In addition, limited availability of low-dose atropine limits the use of atropine as a myopia control strategy. It has been shown that spending more time outdoors acts as a preventive mechanism against the development of myopia. With evidence from studies on children from the region indicating more near work and reduced outdoor time as risk factors for myopia, it is imperative to educate parents and teachers for the need to increase time outdoors.



How to cite this article:
Gammoh YS. Strategies in myopia prevention and management.Sudanese J Ophthalmol 2019;11:1-7


How to cite this URL:
Gammoh YS. Strategies in myopia prevention and management. Sudanese J Ophthalmol [serial online] 2019 [cited 2019 Dec 8 ];11:1-7
Available from: http://www.sjopthal.net/text.asp?2019/11/1/1/268793


Full Text



 Introduction



The seminal paper by Holden et al. estimated that one-third of the world population will be myopic by 2020 and expected that it will reach to 50% by 2050.[1] As we are approaching 2020, myopia in many countries worldwide has already exceeded the estimated prevalence. Myopia in some Asian countries has already exceeded the estimated prevalence in 30 years' time. However, few data exist in relation to the prevalence of myopia in the Middle East. It has been shown that uncorrected refractive error, especially myopia, is one of the main causes of avoidable vision impairment worldwide.[2] As this can be easily rectified with spectacles correction, there is an urgent need to provide accessible and affordable vision-correcting spectacles as this will improve the quality of life and reduce the economic and public health burden.[3]

Various studies have investigated the etiology of myopia and the causes of myopia progression in various parts of the world. There is strong evidence for the role of genetics in the development of myopia, especially high myopia. Parental myopia has been shown as a risk factor for myopia in children. Environmental factors have been implicated in the development and progression of myopia. Increased education and spending more time indoors and more near work have been shown as risk factors, while spending more time outdoors acts as a protective mechanism against myopia development in children.[4],[5] With the increase in myopia prevalence and the strong evidence for environmental factors in myopia development and progression, there has been an interest in attempting to prevent myopia onset and control the progression of myopia. Several myopia control strategies have been investigated including optical methods and use of pharmacological agents in addition to environmental modification with various success rates. Research concerned with myopia control is not reflected fully in clinical practice. Clinicians in Asia are more concerned and involved in myopia control compared to other parts of the world, with no data available from the Middle East. The most prescribed method is single-vision lenses although they have been shown to have no role in controlling myopia progression. The most effective strategies as perceived by clinicians are orthokeratology, followed by environmental modification and use of pharmaceutical agents.[6]

This review identifies studies on myopia prevalence conducted in the Eastern Mediterranean region (EMR) and explores clinically available key strategies investigated in the literature in relation to prevention and management of myopia, with a view on how myopia control can be employed in the region.

 Myopia in the Eastern Mediterranean Region



The EMR, as per the World Health Organization classification, encompasses 22 countries with an estimated 583 million people residing in the region. The following countries belong to the EMR: Afghanistan, Egypt, Bahrain, Djibouti, Iraq, Iran, Jordan, Kuwait, Lebanon, Libya, Morocco, Oman, Pakistan, Palestine, Qatar, Saudi Arabia, Somalia, Sudan, Syria, Tunisia, United Arab Emirates, and Yemen.[7] Very few studies document the refractive error distribution in children or adults in the region. In a study conducted two decades ago in Saudi Arabia investigating the prevalence of refractive error in university students and staff population, approximately 47% of the sample investigated had myopia.[8] A study investigating refractive errors in Jordan using noncycloplegic refraction revealed that approximately 54% of adults aged 17–40 years were myopic.[9] It is of interest that approximately half of the adult population in these countries are myopic, already reaching the projected prevalence in 2050;[1] however, since there are no other population-based studies from other neighboring countries, it is difficult to have full understanding of the prevalence of myopia in the region. A study from Iran, which is geographically and ethnically distant from the above-mentioned countries, revealed that 34% of adults above the age of 15 were myopic.[10] In the same study, myopia was found in 4% of children under the age of 15 years. This is in alignment with estimated projections by Holden et al.[1]

Evidence from other parts of the region provides contradicting results regarding the prevalence of myopia in children. In a study investigating the refractive error status in children between 3 and 6 years of age in Saudi Arabia, myopia was found in approximately 4% of the sample investigated.[11] However, it is to be noted that this study used near-retinoscopy (Mohindra) technique rather than cycloplegic refraction which would overestimate myopia in children. A study conducted on Jordanian schoolchildren revealed that approximately 18% of schoolchildren under the age of 17 years in Amman were myopic, with parental myopia and near work being associated with myopia.[12] Despite the discrepancies in study design, age range of children, and classification of refractive error, the above studies do not provide evidence for an “epidemic” of myopia in children and adults. However, a very recent study from Oman provides evidence regarding the changing in myopia prevalence in schoolchildren in the region.[13] This study shows that myopia has been increasing among schoolchildren in the last few years, with more myopia affecting children at a younger age. This is in agreement with studies from other parts of the world, where increased near work and reduced time spent outdoors being identified as risk factors for the increased incidence of myopia in children at a younger age.[5]

 Myopia Control Using Spectacles



Under-correction of myopia and use of single-vision lenses

Under-correction of myopia has been perceived as a method of controlling myopia progression, due to induced myopic defocus. However, conflicting results do not support this theory and under-correction of myopia is also not recommended clinically.[5] However, many clinicians worldwide still under-correct myopia as a method of myopia control. Indian, Portuguese, Spanish, and South American clinicians practice under-correction more than their colleagues in other parts of the world (e.g., USA and UK).[6] No data are available from the ERM; however, with the similar educational level and scope of practice between those regions and the EMR, it is expected that practitioners in the region would practice under-correction as a form of myopia management. The most accessible and affordable method of correcting myopia is single-vision lenses. This is proven by the fact that over two-thirds of practitioners prescribe single-vision lenses as the primary method of myopia correction.[6] However, evidence shows that single-vision lenses do not play a role in controlling myopia progression.[5] If other forms of myopia control are not available, the minimum the practitioners can offer to their patients is full correction with single-vision lenses to ensure that a clear image falls on the macula.[5],[6]

Progressive addition lenses

Use of progressive addition lenses (PALs) has been suggested almost 20 years ago as a method for controlling myopia progression in children by Leung and Brown.[14] A reduction of approximately half a diopter was observed when using +1.50 D or +2.00 D lenses, which theoretically would reduce the accommodative demand and limit the accommodative lag. Several other studies in different countries revealed that using PALs would reduce the progression of myopia. However, the reduction was <0.25 D and deemed not to be clinically significant.[15],[16],[17],[18],[19] Evidence from short-term and long-term longitudinal studies indicate that PALs can be useful in controlling myopia in children who exhibit accommodative lag or are esophoric. Results from the COrrection of Myopia Evaluation Trial II Study indicate doubling in the reduction of myopia progression (0.41 D vs. 0.28D) when PALs were used in children who had higher lag of accommodation.[19] A 1-year study by Berntsen et al. have shown only 0.18 D reduction in myopia progression.[20]

It seems that the use of PALs reduces myopia progression in children; however, this reduction is very small and is not considered clinically significant. Although no studies are available from the EMR about the habit of prescribing PALs for myopia control, advocating for the use of PALs to control myopia in the EMR would prove controversial based on the evidence from other parts of the world. However, since PALs are available in the EMR and practitioners are familiar with using them for either correcting presbyopia or for occupational use, practitioners may be inclined to prescribe PALs for myopia control in the region.

 Myopia Control Using Contact Lenses



Multifocal contact lenses

Multifocal (MF) soft contact lenses have been available commercially for some time to correct presbyopia. The lenses are available in many designs; the center-distance design aims to correct the refractive error through the central portion while providing more positive power towards the periphery to compensate for the loss of accommodation at near, meanwhile the concentric design provides distance correction and near-correction in defined alternating zones. Although MFs are aimed for presbyopes, they have been used in several studies to investigate their effect in myopia control. A summary of the most recent studies is presented in [Table 1].{Table 1}

Walline et al. found that a 50% reduction in myopia progression using a +2.00 D adds commercially available MF contact lens.[21] A study conducted on Japanese children using a specially designed, nasally decentered with addition of +0.50 D has shown a relatively low rate of myopia reduction.[22] Defocus-incorporated soft contact lenses, which incorporate concentric rings of distance correction and defocus zone providing a near addition of +2.50 D, also provided a similar myopia control effect.[23] Other studies provide different success rates ranging from 20% to 77%.[24],[25],[26] MiSight™ is a daily disposable soft contact lens developed by CooperVision® to be used by children to control myopia progression. The lens has a concentric design of distance vision correcting rings alternating with a 2.00 D myopic defocus regions. This lens has been showing to produce a clinically significant reduction in myopia progression.[27] MF contact lenses in distance-center designs are available in the EMR and can prove to be useful if prescribed by practitioners for use by children. Many optometrists in the region are not allowed to examine or fit children, and it is the responsibility of the ophthalmologist to educate parents/guardians about the availability of MF contact lenses and their potential benefit in controlling myopia. To the best of the author's knowledge, MiSight™ is not yet available in the EMR.

Orthokeratology

Corneal reshaping contact lenses have been used to temporarily reshape the cornea during overnight wear to provide a clear correction-free vision during the day. Orthokeratology is a term used for the overnight wear of corneal reshaping contact lenses, and it has seen resurgence in the past few years due to advances in lenses design and material.[28] The Corneal Reshaping And Yearly Observation of Nearsightedness Study investigated the 2-year effect of wearing orthokeratology lenses on the changes in axial length measurements compared to a control group wearing single-vision contact lenses.[28] Orthokeratology lenses have proved to reduce the progression of axial length in comparison to single-vision lenses which would indicate their usefulness in managing the progression of myopia. Another study compared the 2-year effect of orthokeratology lenses to single-vision spectacles and reached to a similar conclusion.[29] Hiraoka et al. investigated the effect of orthokeratology over 5 years and found similar results in the first 3 years of the study while observing minimal effect in the 4th and 5th year.[30] This is an interesting observation as many studies involving various control strategies are limited to 2 years and few long-term data on efficacy of these strategies are available. Other recent studies that were also limited to a 2-year study period reported reduction in axial length progression in the orthokeratology wearing group compared to the control group.[31],[32],[33] A summary of the most recent studies related to use of orthokeratology lenses is presented in [Table 2].{Table 2}

Most clinicians have identified orthokeratology as an effective method of myopia control with cost and safety as main concerns or reasons not fit this type of lenses.[6] Fitting orthokeratology lenses requires the use of special equipment, such as a corneal topographer, to determine the needed parameters or having an extensive trial set to identify the ideal fit. Many optometrists in the EMR do not have access to corneal topography in their clinical practice and require referral to specialty ophthalmic centers which would add to the cost of the lens fitting. Monitoring the efficacy of orthokeratology required the use of axial length measuring instruments, which are not also readily available in optometry practice in the region. Continuous referral to specialty clinics to monitor axial length progression may prove costly and might deter the family of the child to use orthokeratology as a myopia control strategy.

 Use of Atropine in Myopia Control



Atropine sulfate is an antimuscarinic agent that inhibits the action of smooth muscles innervated by cholinergic receptors. It is used in the 1% concentration for cycloplegia, mydriasis, and amblyopia therapy. One of the first randomized controlled trials that investigated the use of 1% atropine was the Atropine for the Treatment Of childhood Myopia Phase 1 (ATOM1) study.[34] ATOM1 investigated the use of atropine in 400 children in Singapore aged 6–12 years with myopia ranging from −1.00 D to −6.00D. The study included the use of atropine for 2 years with 1 year of not using atropine, known as a “washout year.”[35] To reduce the effects of glare and blurring at near, all children were prescribed photochromic PALs. After 2 years of treatment with atropine, a significant reduction in myopia progression while a “rebound” effect was noticed after the washout period where a significant increase in myopia progression was noted after stopping treatment for 1 year.[35]

The ATOM2 study followed the ATOM1 study where the effect and safety of 0.5%, 0.1%, and 0.01% atropine were investigated.[36],[37],[38] Many children using the 1% atropine complained of glare and near-vision difficulties, while very few children who used the 0.01% experienced these issues. In terms of efficacy in managing myopia, the 0.01% was comparatively similar in providing clinically significant reduction in myopia progression, while showing the least rebound effect. Other studies investigating the use of atropine in myopia control are summarized in [Table 3]. All the studies indicate that atropine is useful in controlling myopia progression with the lowest dose (i.e., 0.01%) to be clinically effective with the least complication experienced by the users.[39],[40],[41] Use of atropine in myopia control is a strategy that can be employed in the EMR; however, several difficulties might not prove atropine to be a popular choice by either clinicians or children and their parents. Atropine 1% is readily available; however, with the increased complications and dropout rate, it is advised to use the 0.01% which is not available commercially and needs to be compounded by a pharmacist. Availability of pharmacists that can compound atropine and cost and hygiene are the issues to be concerned. Even if 0.01% is available, the added cost of photochromic PALs may prohibit many families from providing their children with atropine as a strategy to control the progression of myopia. In addition, the accumulative effects of using low-dose atropine are still unknown; further studies are needed to ensure its long-term safety.{Table 3}

 Role of Outdoor Activities in Myopia Prevention and Control of Progression



Several studies have investigated the role of outdoor activities in preventing the onset of myopia or delaying the progression of myopia.[5] However, very few randomized controlled trials have investigated the role of outdoor activities; the main results of these studies are summarized in [Table 4]. Wu et al. investigated the role of incorporating outdoor activities in the school system in the form of a recess outside classroom.[42] The intervention proved to be effective in delaying the onset of myopia. The Guangzhou Outdoor Activity Longitudinal Trial investigated the incorporation of additional 40 min of outdoor activities at the end of school day.[43] The study has proved effective in reducing the onset of myopia with around 9% reduction in the incidence of myopia. Jin et al. conducted a large-scale study where extra time outdoors in the form of recess outside classroom has proven to reduce the onset of myopia incidence by 4.8%.[44] In a more recent study in Taiwan, students were encouraged to spend about 11 h/week conducting outdoor activities in 1000 lux level of light.[45] Increasing time outdoors has also been effective in reducing the incidence of myopia and reducing the risk of myopia progression in already myopic children. The studies mentioned above have also reported a reduction in axial length growth. Although outdoor activities have proven to be effective in preventing myopia onset, the mechanism of controlling the onset of myopia is still unclear. Several factors have been suggested such as the depth of focus induced by pupil constriction, dopamine release, and Vitamin D levels, with no currently accepted mechanism of action.[5] Advocating for outdoor activities during the school time in the form of recess outside classroom and encouraging the children and families to spend more time outdoors and reduce the time spent indoors on near work activities need to be advocated in the EMR.{Table 4}

 Conclusion



The scarcity of studies on the prevalence of myopia including high myopia in the EMR does not allow the stakeholders involved in the eye-care of the nation to have a clear strategy or clinical guidelines in relation to myopia management. Many strategies in regard to myopia control have been investigated, with various success rates being reported. Strategies employing MF contact lenses and corneal reshaping therapy (i.e., orthokeratology) have proven to be successful in controlling myopia in children. However, MF contact lenses are not prescribed to children in the EMR, and the limited scope of practice imposed on optometrists in the region is a barrier against advocating the use of these lenses in the region. Fitting orthokeratology lenses requires specialized equipment such as corneal topography, while monitoring myopia progression in children wearing orthokeratology lenses requires instruments that measure the axial length of the eye. As such equipment does not exist in most high street optical centers, this will limit the use of these lenses to specialized ophthalmic centers. Many ophthalmology clinics rely on referral to specialized centers for obtaining corneal topographic maps or axial length measurements which can add more costs to the procedure, which requires constant monitoring by an eye care professional. Involvement of authorities and optical industries is important to ensure the success of myopia control program in any country. Their involvement may help to control the price of lenses (MFs/orthokeratology), which would increase the lenses penetration in the market. Many children are spending more time indoors due to changes in lifestyle, including the plethora of digital devices available to children nowadays. Outdoor activities have shown to have a protective mechanism against myopia development in children across many parts of the world. Since many myopia control strategies are not available or accessible in the EMR, all stakeholders in the region need to advocate for outdoor activities for children from an early age prior to the onset of myopia.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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