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Concern for myopia progression increases with alarming rise in global prevalence
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The prevalence of myopia, one of the most common eye disorders across the world, has alarmingly increased over the years, starting at younger ages than ever before. A systematic review and meta-analysis recently published in Ophthalmology estimated that myopia and high myopia will affect nearly 5 billion people and 1 billion people, respectively, by 2050.
Studies of East Asian populations report a two-, three- or even fourfold increase in the number of teenagers and young adults developing the disorder. In Singapore, China and Korea, current rates are between 85% and 96%.
In the U.S., myopia has nearly doubled in the last 30 years, going from a 25% prevalence rate in 1971 to 1972 to a 42% prevalence rate in 1999 to 2004. Europe has similar patterns and similar rates, as shown by a study published in 2015 by the European Eye Epidemiology Consortium in Ophthalmology.
“This European study looked at the prevalence of myopia in two different cohorts, those born before and after the 1940s. We found that the overall prevalence after the 1940s is significantly higher. In addition, the rate of myopia in younger individuals of this group is now approaching 40%, while in the older adults is 20%. Prevalence has doubled in a time period of just over one generation,” Katie Williams, MBChB, FRCOphth, first author of the study, said.
Myopia is widely regarded by the majority of ophthalmologists as a simple optical inconvenience that is easily correctable. But such a high growth rate, with an estimated 227.2 million people across Europe affected, calls for a change of perspective.
Image: Williams K
“We need to become aware that we are dealing with an epidemic, that this has implications in terms of associated vision-threatening pathologies and economic burden, and that prevention of onset and control of myopia progression are a high priority,” Williams said.
‘A true disease’
“First of all, we have to recognize that myopia is not only a refractive problem, but a true disease. Comorbidities related to the abnormal stretching of the eye, such as retinal detachment, neovascularization, early cataract and glaucoma, are major causes of visual impairment and blindness,” Dominique Brémond-Gignac, MD, PhD, OSN Europe Edition Board Member, said.
Early onset of myopia is associated with progression, leading to high myopia in a significant number of cases. Southeast Asia is again on the frontline, with high myopia ranging between 21% and 40% in the myopic population.
“The more myopic prevalence increases, the more the percentage of patients end up with high myopia. And it is the high myopia group that is most likely to develop ocular comorbidities or significant ocular problems in adulthood,” Donald T.H. Tan, MBBS, FRCSG, FRCSE, FRCOphth, OSN APAO Edition Board Member, said.
Genetic and environmental factors
While in the past myopia was regarded as a genetically inherited condition, today’s research is focusing on the interaction between genetic and environmental factors.
“There are at least 30 chromosomes associated with myopia, and genetic research may lead to interesting developments in the future. What has clearly come out in the latest years is that a strong correlation with environmental factors also exists. Education, increased use of near vision, and early and prolonged use of computers, tablets and mobiles are likely to be at the origin of the epidemic growth of myopia we are witnessing now,” Lucio Buratto, MD, OSN Europe Edition Board Member, said. “As for many conditions, there is a predisposition, a genetic basis, and then there is a very complex interaction with environmental risk factors.”
Williams was involved with the European Eye Epidemiology Consortium in another study, looking at education as a risk factor for myopia.
“We found that the myopia rate was almost double in individuals completing higher education compared to those who had left school at the age of 16,” she said.
Education involves more time spent inside, while several studies have demonstrated the protective effect of outdoor activities against myopia. Education also involves reading books and using computers.
In Williams’ opinion, however, this factor alone cannot explain the rising trend.
“Interestingly, there is evidence that people with higher achievements in school, people with a high IQ, tend to have more myopia. This might bring us back to genetics,” she said.
Preventing progression
According to a review published in Adolescent Health, Medicine and Therapeutics, myopia typically develops at approximately 8 years of age and progresses by approximately 0.5 D per year until the age of 15 to 16 years. Conversely, those who develop myopia later in life do not face as severe a progression rate as adolescents.
“Early onset is a serious problem and the cause of major progression. However, if it is screened early, myopia progression can be slowed down,” Brémond-Gignac said.
Results from clinical trials for outdoor intervention programs to reduce incident myopia have shown promising results. The recently released Myopia Consensus Statement of the World Society of Paediatric Ophthalmology and Strabismus (WSPOS) recommends increasing daylight exposure and reducing intense periods of near work. Pediatric associations in some Asian countries recommend not exposing children to television or other screens before the age of 2 years.
“Over the years, we have learned what not to do. In the past, we used to undercorrect myopic children, and now we know that undercorrection actually induces myopia because the myopic defocus in the periphery of the retina increases the axial length. We must make sure that myopic children always have the best correction and should therefore be monitored closely, every 3 to 6 months,” Brémond-Gignac said.
Pharmacological strategies
Varying concentrations of atropine eye drops and orthokeratology have been further studied in recent years as treatments that may slow myopia progression.
“With atropine the problem really is twofold, whether there are systemic side effects with atropine as a cardiac drug and whether there are any topical side effects,” Tan said.
The Atropine for the Treatment of Myopia (ATOM2) clinical trial, published in Ophthalmology, compared the safety and efficacy of different concentrations of atropine eye drops to control myopia progression over 5 years.
In the double-masked study, 400 children were randomized 2:2:1 to receive 0.5%, 0.1% or 0.01% of atropine once daily in both eyes for 2 years. Children who received higher concentrations of atropine initially demonstrated a greater effect in slowing myopia progression; however, there was no significant difference between dosage groups at 2 years. The 76% of children who did not require re-treatment in the 0.01% group after year 3 continued with a persistent response in reduced progression; had the lowest overall myopia progression and change in axial elongation; and had minimal pupil dilation, minimal loss of accommodation and no near visual loss compared with the higher concentrations of atropine at the end of the 5-year follow-up.
Tan said he believes the 0.01% concentration has minimal side effects while still reducing the rate of myopia progression by 50% to 60%.
“The average pupil dilation is about 1 mm, which we don’t think is that clinically significant,” Tan said. “Very few children, if any, will get glare. And there is minimal effect on accommodation, so children with this lower dose have actually no problem in reading and studying.”
In the WSPOS consensus statement, atropine 0.01% is No. 1 in the list of “What does work” in retarding progression of myopia. It “appears to offer an appropriate risk-benefit ratio, with no clinically significant visual side effects balanced against a reasonable and clinically significant 50% reduction in myopia progression,” according to the document.
Tan said more studies are needed to make management options more customizable because “one size doesn’t fit all.” He recommended reviewing atropine with adjunctive treatments.
“For example, you could use atropine eye drops and some of these optical aids like contact lenses or bifocals/spectacles, as well as environmental and behavioral modifications — get parents to make sure the child has outdoor activities. This needs to be done, but it’s many more years of work,” he said.
Optical strategies
A study, published in Eye & Contact Lens, reviewed 170 publications to evaluate the ocular safety of orthokeratology treatment to correct and delay myopia. Potential complications significantly associated with orthokeratology included microbial keratitis, corneal staining and lens binding; however, the study authors found it to be a generally safe treatment option.
The WSPOS consensus document noted that orthokeratology results in an approximately 40% reduction in the progression of myopia, although sustained myopia control is still unproven and no washout data are available. Some concern, however, is expressed about the “more than one hundred cases of severe microbial keratitis related to orthokeratology” reported since 2001.
Brémond-Gignac said she does not give the option of orthokeratology, “not only because of the risk of infection but because it may cause damage to the limbus,” she said.
Correction strategies
Optical correction of myopia has greatly improved in recent years with new materials for spectacles and contact lenses. Refractive surgery also offers a range of safe and effective options.
“The eye remains a myopic eye with correlated problems, but we can improve vision and life quality,” Buratto said.
Precise diagnosis and accurate evaluation of individual patients are mandatory. In patients up to the age of 45 years with sufficient corneal thickness, laser photoablation gives excellent results. Phakic IOLs can be used up to the age of 50 years, and then lens surgery with implantation of trifocal IOLs can compensate for the loss of accommodation.
“It is important to wait until myopia has stopped progressing and is stable, which in most cases happens around the age of 22. I have quite a few young people who come earlier, but I accept them only in special cases and ask to talk to the parents as well,” Buratto said.
On the other hand, there is increasing demand for refractive surgery by older people in the baby boomer generation.
“They are used to a very active life, work, travel, use technologies, care for their appearance and want life quality. And good vision is essential for life quality,” Buratto said.
Refractive surgery of any kind has an immediate great impact on myopes and changes their lives.
“If you have a good eye and a motivated patient, it’s a done deal. When I operate on myopes and arrive at the office for the day 1 visit, the smile I see on those faces is the best reward I could ever get,” Buratto said. – by Michela Cimberle and Kristie L. Kahl
- References:
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- Morgan IG, et al. Lancet. 2012;doi:10.1016/S0140-6736(12)60272-4.
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- Wolffsohn JS, et al. Cont Lens Anterior Eye. 2016;doi:10.1016/j.clae.2016.02.005.
- World Society of Paediatric Ophthalmology & Strabismus Myopia Consensus Statement. http://wspos.org/wp-content/uploads/2016/04/WSPOS_Consensus-Statement_Myopia.pdf.
- For more information:
- Dominique Brémond-Gignac, MD, PhD, is head of ophthalmology at the University Hospital Necker Enfants Malades in Paris. She can be reached at Hôpital Necker-Enfants Malades, 149 rue de Sèvres 75015, Paris, France; email: dominique.bremond@aphp.fr.
- Lucio Buratto, MD, is director of the Centro Ambrosiano Oftalmico di Microchirurgia Oculare. He can be reached at Centro Ambrosiano Oftalmico, Piazza Repubblica, 21 - 20124 Milano, Italy; email: iol.lasik@buratto.com.
- Donald T.H. Tan, MBBS, FRCSG, FRCSE, FRCOphth, is senior advisor of the Singapore National Eye Centre and chairman of the Singapore Eye Research Institute. He can be reached at Singapore National Eye Center, 11 Third Hospital Avenue, Singapore 198751; email: donald.tan.t.h@snec.com.sg.
- Katie Williams, MBChB, FRCOphth, is a clinical research fellow at St. Thomas’ Hospital, King’s College London. She can be reached at email: katie.williams@kcl.ac.uk.
Disclosures: Brémond-Gignac, Buratto, Tan and Williams report no relevant financial disclosures.
Is it time to consider atropine as first-line therapy to reduce progression of myopia?
Low dose is effective
Yes, it is time to consider atropine as first-line therapy in children with progressive myopia. There has been increasing evidence in recent years that environmental factors such as near work and a shift away from outdoor activities play a key role in the development of myopia. The first studies on atropine as a means to slow progression were done in Southeast Asia, where myopia prevalence has grown to epidemic proportions. From the first 1% dosage, which proved effective, concentrations have been progressively lowered. In the latest ATOM clinical trial, a minimal 0.01% concentration has shown comparable results, with no dilating effects and no discomfort. It is clear now that the positive outcome of the treatment was not due to pupil dilation, which discouraged near work, but to the effect of atropine on dopamine release and consequently eye growth.
Personally, I have seen atropine 0.01% work in 65% of the children I treat, who are probably those in which myopia is prevalently due to environmental factors. As soon as I see the onset of myopia, usually around 8 years of age, and a control visit confirms that progression is equal of more than 0.75 D in 1 year, I propose low-dose atropine to the parents. Treatment is carried out for 2 years, stopped for a short washout period of 3 to 6 months and then continued for another 2 years. This takes the child thorough the crucial time of puberty and consistently reduces myopia progression with no side effects.
Paolo Nucci, MD, PhD, is a pediatric ophthalmology specialist, professor and head of San Giuseppe Eye Hospital, University of Milan, Italy. Disclosure: Nucci reports no relevant financial disclosures.
More work is needed
More work is needed before atropine can be considered a first-line therapy to reduce progression of myopia. The ATOM1 study documented an average of only –0.29 D progression of myopia over 2 years in the 1% atropine group. However, visual function suffered, and side effects made the treatment unpopular. ATOM2 showed, surprisingly, that very dilute atropine (0.01%) can still slow myopia progression, although not as markedly as the 1% solution (average progression of –0.49 D). This very dilute solution has not been adequately tested across a diverse patient population, and it is not commercially available in the U.S. While compounding pharmacies can mix it, a short shelf life may make it difficult to stock and costly to dispense. In addition, the optimal duration of use has not been worked out, and rebound myopic progression after discontinuation may reduce the long-term benefit. Atropine use has not been linked, thus far, with a reduction in the most serious side effects of high myopia (myopic maculopathy and retinal detachment). Optimal treatment strategies will require not only a more complete understanding of atropine’s effects on axial eye growth, but also the consequences of and remedies for relative peripheral hyperopia, accommodation errors and the indoor visual environment of children with myopia.
M. Edward Wilson, MD, is an OSN U.S. Edition Pediatrics/Strabismus Board Member. Disclosure: Wilson reports no relevant financial disclosures.