|Year : 2022 | Volume
| Issue : 1 | Page : 17
Myopia is progressing faster than its management options
Department of Clinical Ophthalmology, Institute of Ophthalmology, University College London, London, United Kingdom
|Date of Submission||16-Nov-2021|
|Date of Decision||03-Jan-2022|
|Date of Acceptance||03-Feb-2022|
|Date of Web Publication||25-Mar-2022|
Dr. Ali Nouraeinejad
Department of Clinical Ophthalmology, Institute of Ophthalmology, University College London, London
Source of Support: None, Conflict of Interest: None
Myopia, as the most common source of distance vision impairment in the world, is a serious global public health and socioeconomic crisis. Although more than half of the world population will be myopic by 2050, none of the myopia control strategies has been demonstrated to completely stop the development or progression of myopia. This is due to the fact that myopia is progressing faster than its management options. It should also be emphasized that none of the current myopia control strategies is practically in use for some reason except for research purposes. It is of critical importance to realize that without any effectual controls or therapeutic interventions, myopia crisis enlarges further.
Keywords: Environmental factors, genetics, myopia control, myopia progression, myopia
|How to cite this article:|
Nouraeinejad A. Myopia is progressing faster than its management options. Pan Am J Ophthalmol 2022;4:17
| Introduction|| |
Myopia is generally defined as “a refractive condition of the eye in which parallel rays of light entering the eye are brought to a focus in front of the retina when the ocular accommodation is relaxed.”,,
Myopia is a serious global public health and socioeconomic crisis.,,,, Recent analyses of 145 studies regarding the global prevalence of myopia and high myopia have shown that 28.3% and 4.0% of the world population have myopia and high myopia, respectively, and these figures are expected to boost to 49.8% and 9.8% of the world population for myopia and high myopia, correspondingly by 2050.,,,, This will include 4758 million people for myopia and 938 million for high myopia by 2050.,,,, These trends will be enough to worry about to realize how big the problem is.,,,,
To clarify a few important basic descriptions, in the beginning, it is worth mentioning that the definitions of “myopia,” “high myopia,” and “pathologic myopia” have not been standardized. For example, the term “pathologic myopia” is frequently confused with “high myopia.” However, “high myopia” and “pathologic myopia” are distinctly different. “High myopia” is defined as an eye with a high degree of myopic refractive error so that the spherical equivalent refractive error of an eye is equal or larger than − 6.00 D when ocular accommodation is relaxed, and “pathologic myopia” is defined as a myopic eye with the presence of pathologic lesions and degenerative changes in the posterior fundus.
It is also important to learn that pathologic myopia is a major source of blindness or vision impairment in both Asian and Western countries,,,,,, so that over 200 million people will be affected by pathologic myopia by 2050., The main basis of blindness in patients with pathologic myopia comprises “myopic maculopathy with or without posterior staphyloma,” “myopic macular retinoschisis,” and “glaucoma or glaucoma-like optic neuropathy.” The term “pathologic myopia” represents the condition of pathologic consequences of a myopic axial elongation. In a current consensus, pathologic myopia was identified as “myopic chorioretinal atrophy equal to or more serious than diffuse atrophy” and/or “the presence of posterior staphylomas.”, It is also unfortunate to be informed that currently practised treatment methods against pathologic myopia have not been totally effective in stopping the pathological progression., However as it was defined earlier, there are many types of myopia and not all myopic individuals go blind.
| Myopia in Children|| |
There are plenty of documents showing myopia mostly develops in school-age children so that the prevalence of myopia begins to rise after the age of 6 years when the schooling starts.,,,,, The development of myopia in school-age children has been demonstrated to be related with various factors including Asian ethnicity,, parental history of myopia,, reduced time spent outdoors, and increased level of near-work activity., The majority of increased myopia onset was shown to be related to increased educational intensity. This highlights an important role for policymakers to balance educational achievement and myopic interventions to prevent myopia progression, especially in East Asia. This can be tough to manage in East Asian countries and surely requires a collaborative effort among clinics, schools, parents, and the entire society.
| Etiology of Myopia|| |
Any disruption to the highly coordinated ocular changes during the process of emmetropization, an active regulatory process that harmonizes the expansion of the eye with the optical power of the cornea and the crystalline lens, leads to the development of refractive errors during the early period of visual development.
The quality of the retinal image of visual environment also modulates the refractive development of the eye throughout the visual experience both in the early period of visual development or even later in life. Ocular response to form-deprivation and lens-induced defocus is evident across a wide range of animal species, including humans.
Myopia is a highly heritable trait, along with environmental influences, such as increased near work and insufficient outdoor activity acting significant parts in its development and progression. Based on the visually guided ocular growth mechanism, relative peripheral hyperopia in corrected myopia provokes axial elongation in order to reduce relative peripheral hyperopia in these cases.
The prevalence of myopia in children, teenagers, and young adults is significantly higher in urban East Asian countries compared with other countries.,,, However, the prevalence rates of myopia in adults in urban East Asian countries are just slightly higher than in Western countries., This brings the possibility of increased educational intensity as a factor for myopia progression in East Asian countries during recent years. Generational differences in the prevalence of myopia and high myopia have been documented with the highest rates in young adults and the lowest rates in older adults. This may be due to generational differences, or changes in the lifestyle components, such as the type of educational system, intensity of near work, and outdoor time exposure in rapidly developing urban settings in many Asian countries. These documents are supportive as the evidence that myopia is not caused by purely genetic differences.,
These various potential causes of myopia development are the main factors for different treatment options in myopia.
Genetics of myopia
The propensity for myopia to occur in families has long been documented, indicating the role of genetic factors in discovering the total risk. Myopia is extremely heritable,,,,,,,,,,,,,,, so that genes explain up to 80% of the variance in refractive error in twin studies. However, clinical implications obtained from genetic analyses of myopia are limited at present. This is in view of the high polygenicity of myopia and low explained phenotypic variance by genetic factors (7.8%). Gene–environment interaction analyses are ongoing to evaluate whether genes act differently across different environments.
Key environmental factors on myopia
Consistent results of both cross-sectional and longitudinal studies regarding evidence of insufficient time spent outdoors as a risk factor for myopia progression have been presented.,,,,,,,,,,,,,,,,, In this regard, the randomized clinical trial in Guangzhou found that an additional 40 min of outdoor activity can diminish the incidence of myopia by 23%. Other trials also found that an extra 80 min may further reduce the incidence of myopia by 50%., These studies have proved a dose-dependent effect of time spent outdoors in the prevalence of myopia. Therefore, the duration of outdoor activities is also influential.
Different reasons for the protective efficacy of time spent outdoors in myopes have been suggested. These probable reasons include higher light intensities, differences in chromatic composition, the reduction in dioptric accommodative focus and psychometric influences encountered outdoors, and the role of chromaticity (red and blue) and ultraviolet light. Outdoor activity and/or bright light were also shown to inhibit myopia, potentially through increased dopamine and vitamin D levels.
Near work and education
Near-work activity as a risk factor for myopia has been proved.,,,,,, Many studies have also confirmed a strong association between myopia and education.,,,,, In this regard, exposure to longer duration of education was found to be a causal risk factor for myopia.
Optical, or biomechanical, ocular changes associated with near-work activities have been suggested as the reasons for advancing myopic eye growth in those myopic individuals with higher levels of education, which can demand higher near-work requirements.,,
| Correction and Control of Myopia|| |
Myopia can be corrected by several ways including spectacle lenses, contact lenses, and laser surgeries and these methods have been established for ages. The correction of myopia to induce clear vision has been successful. There are currently many eye surgeries to correct myopia. These include laser in situ keratomileusis (LASIK), laser subepithelial keratomileusis, wavefront-based excimer laser refractive surgery, photorefractive keratectomy (PRK), epithelial LASIK, intrastromal corneal ring segments, small incision lenticule extraction, phakic intraocular lenses, and refractive lens exchange with implantation of multifocal or monofocal intraocular lenses.
Advanced ocular imaging is also vital to discover complications of pathologic myopia in order to start both medical and surgical interventions as part of their management.
On the other hand, to control the myopia progression, there are many forms of preventive interventions including bifocal spectacle lenses,, progressive addition lenses,,,,,,,, special spectacle lens with defocus incorporated multiple segments (DIMS),,,, spectacle lens designed to reduce relative peripheral hyperopia,, soft contact lenses, rigid gas permeable contact lenses,, soft bifocal and multifocal contact lenses,,,,,, orthokeratology (Ortho-K),,,,,,,, pharmaceuticals,,,,, and environmental or behavioral modification.,,,,,,,, For example, children aged 8–13 years who wore special spectacle lenses with DIMS were shown to have about 60% less myopia progression and axial elongation compared with children wearing single vision spectacle lenses over 2 years. Another example is the application of soft bifocal and multifocal contact lenses, which has shown to slow the progression of myopia in children by an amount comparable to that of Ortho-K lenses. In this regard, the effect of these bifocal soft contact lenses has shown to slow myopia progression by 25%–50% and axial length by 27%–32% in children aged 8–16 of an assortment of ethnicities over a period of 24 months., Combination therapy of different methods (e.g., the combination of Ortho-K and low-concentration atropine [0.01%] eye drops) has also been tried so that the combination of Ortho-K and low-concentration atropine (0.01%) eye drops was shown to be more effective in slowing axial elongation over 12 months than Ortho-K treatment alone in myopic children.
Pharmaceuticals have also been tried to slow myopia progression. One of these pharmaceuticals has been the usage of different doses of atropine (1.0%, 0.5%, 0.1%, 0.05% or less).,,,,,,,,, The efficacy of atropine in myopia control was found to be dose related so that 0.05% atropine has been reported to be the optimal dose., While high doses of atropine (i.e., 0.5% or 1.0%) were shown to slow myopia progression by more than 70% in Asian children aged 6–13 years over 1–2 years,,,,, lower doses (0.1% or less) were also reported to slow myopia progression by 30%–60% with less side effects (pupil dilation, glare, or blur). However, a myopic rebound has also been reported if atropine was abruptly stopped, especially at higher doses and in younger children.,
In addition to all of those above-mentioned documents regarding myopia control, there are many others explaining the benefit of different forms of interventions for myopia control.,,,, However, none of these myopia control strategies has been unfortunately shown to fully stop the development or progression of myopia. There have even been some adverse reactions for some of these control methods. For instance, the risk of infective keratitis remains high for contact lens users or those individuals who try Ortho-K.
| Myopia is Progressing Faster than its Management Options|| |
Unfortunately, myopia is progressing faster than its management options. This is simply due to the fact that none of the current myopia control strategies has been unfortunately shown to fully stop the development or progression of myopia while myopia keeps on striking millions of people worldwide. As the global health burden of myopia continues to boost, the myopia control strategies are still on the rocks. Therefore, this calls for newer effectual controls or therapeutic interventions to combat the crisis. In spite of that, it should also be emphasized that none of the current myopia control strategies is practically in use for some reason except for research purposes. The lack of usage of these preventive approaches and methods is going to worsen the myopia crisis as they have at least shown to be effective to some extent in many studies.
It is of critical importance to realize that without any effectual controls or therapeutic interventions the percentage of myopes and high myopes in the world will reach up to 50% and 10%, respectively by 2050. For this reason, effective controls or beneficial interventions, such as more time spent outdoors and less near-work activities should be part of the management options leading to delayed onset of myopia and have the potential to make a noteworthy difference on the future myopia epidemic.
Moreover, emerging infectious diseases (EIDs), such as coronavirus disease-2019 and influenza A virus subtype H1N1 have been shown to indirectly lead to the progression of myopia. In view of the fact that these EIDs are repetitively developing worldwide, they are anticipated to affect the behavior of people pressurizing them to stay more often at home and this is going to come about quite often in the future. Therefore, this will add more chances of getting myopia in the future due to the association of myopia progression and near work imposed by home quarantine.
| Conclusion|| |
Myopia is a serious global public health and socioeconomic crisis. Even supposing that no clear-cut management options have been established so far to fully stop myopia progression, success has been accomplished in slowing the rate of progression via optical and pharmaceutical intervention strategies as well as time spent outdoors and behavioral influences. That is why there should not be any hesitation to put these preventive procedures into practice in the course of policies and approaches. Otherwise, the myopia crisis will be worse than expected in the future. This is simply due to the fact that myopia is progressing faster than its management options.
The author would like to express his honest gratitude and high respect for the lifetime support of his father, Mohammad Nouraeinejad.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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