May 14, 2019
By Kevin Chan, OD, MS, FAAO
The prevalence of myopia and high myopia are increasing in the U.S. and globally at an alarming rate, with significant increases in the risks for vision impairment from pathologic conditions associated with high myopia, including retinal detachment, myopic macular degeneration, cataract, and glaucoma. Over 30 percent of the world is currently myopic, and by 2050, almost 50 percent will be myopic … a staggering 5 billion people. The US has an estimated overall prevalence of 42 percent in the 12 – 54-year-old age group, almost doubling in three decades. In children and teenagers ages 12-17, the total U.S. prevalence of myopia is estimated to be a shocking 34 percent1,2.
The alarming progression of myopia in East Asia has resulted in more than 20% of the population to develop pathologic myopia 6,7. The public health consequences of myopia have become far too serious to be neglected, considering the increasing risks of vision-threatening complications and global economic burden associated with myopia. Notably, myopic macular degeneration has shown to severely impact visual impairment and functioning 3,4,5, which indirectly resulted in a massive loss of productivity worldwide 8.
Managing low myopia in young adults who continue to progress more than 0.50D per year past age 18
The onset age of myopia among children and adolescents is directly linked to its rate of progression 9,10, which can potentially be predictive of further myopia development in adulthood. While it has been commonly perceived that myopia stabilizes upon cessation of growth spurts as early as age 15 12, interestingly, recent research has found that age at axial length (AL) stabilization lacks association with gender, ethnicity, or number of myopic parents 11. In other words, AL may increase past puberty and continue elongation during adulthood, resulting recurrence of myopia progression.
While young children with predisposing risk factors of myopia, such as two myopic parents, Asian descent, are more likely to develop higher myopia in adulthood 13,14, it is not uncommon to notice young adults with low myopia continue to experience a gradual relapse of myopia progression, yet generally at a relatively slower pace. This growing trend was found to more likely to develop signs of posterior degeneration of the retina 4,6,15.
Undoubtedly, gene-environmental interactions play a vital and definite role in myopia development 16-19. In particular, the study by Tideman et al. found that genetic loci relating to myopia likely exert its effect as a function of age among children, adolescents, and adults 15. Among these three age categories, the adult group aged 25 or above have shown to have the highest number of loci associated with AL and corneal radius (CR). This suggests that myopia development and progression in adults likely occur more commonly than previously expected.
I am often asked about whether young adults showing progressive myopia can be treated with overnight orthokeratology lenses. While young adults are generally more inclined to excel better with orthokeratology lenses because of greater dexterity and tolerance, they also have higher expectations for the quality of vision compared to children. The overall treatment outcomes associated with orthokeratology lenses are primarily influenced by patients’ motivation, compliance, and wear time. Be mindful when selecting young adult patients with type-A personality and fluctuating sleep schedule. Extensive education and discussion with adult progressive myopes before initiating treatment is crucial in developing an understanding of their preferences and expectations. Orthokeratology treatment for adult progressive myopes has shown to successfully reduce, or in some cases halt, refractive error and axial elongation progression, even upon discontinuation of treatment 23.
Managing myopia in a 22-year-old professional student with adult-onset myopia
In comparison to early onset of myopia in children and adolescents, emmetropic adults who suddenly experience myopic spike, especially when they are in graduate or professional studies, are particularly intriguing. Studies have shown that ocular biometric factors, such as diurnal choroidal and quadrant-specific macular thickness, are significantly varied in young adult myopes compared to emmetropes 21,22,33,33. For young professionals who were formerly emmetropic, increased number of years of education has shown cumulative effects in the higher incidence of myopia development in adults, but not in opposite manner 20. It is essential to evaluate these patients with a comprehensive cycloplegic examination and rule out the likelihood of pseudomyopia. Given the extensive demand of near work activities, young adults are likely to be susceptible to the aftereffects of nearwork, which can be a precursor to adult-onset myopia progression 24.
For cases like this, I typically prescribe soft contact lenses with a center-distance multifocal (MF SCL) design for new adult myopes since they are generally better accepted due to its convenience and excellent comfort. Nevertheless, MF SCL for myopia management is not without drawbacks. In the presence of peripheral plus power, the quality of vision may temporarily be affected with glare and low contrast sensitivity during initial adaptation 27,28. While these transient symptoms are generally well tolerated in the pediatric population, young adult myopes may view them as nuisances for which likely affect the overall adaptation and compliance. Typically, these symptoms subside in 1-2 weeks. Therefore, it is advisable to educate young adult patients about potential vision and glare adaptation with MF SCL and establish a realistic expectation for them.
In addition, the binocular vision function in young adults plays a crucial role in determining patient candidacy for myopia control treatments. Studies by Gifford et al. have shown that young adult myopes wearing orthokeratology lenses tend to display greater exophoria and lower accommodative lags compared to single-vision contact lens wearers 25,26. This explains why orthokeratology treatment may benefit young adult myopes with binocular vision dysfunction.
In the event of myopia progression that does not respond well to monotherapy treatment with an optical approach, low-dose atropine in combination with contact lens modality may be warranted. Despite a concentration-dependent response in slowing myopia progression and axial elongation in children 31, clinical efficacy of atropine in adult myopes is yet to be fully tested. In my experience, low-dose atropine, as little as 0.01%, is generally not considered as the first-line monotherapy treatment for young adults since they tend to be more noticeably impacted by the potential unwanted side effects of pupillary dilation and glare 29,30, as compared to children.
When considering treatments for myopia management for young adults, it is essential to understand that this demographic generally represents young millennials with high education level and increased demand for the quality of vision. Optical approaches, such as orthokeratology and soft MF contact lenses, provide convenience and independence from glasses. Nevertheless, clinicians should also be mindful when setting realistic goals and expectations for each treatment. Given the long waking hours for school and work activities, visual clarity and stability are vital components in determining treatment success for young adults. Patients with variable sleep schedule or atypical work schedule (e.g., night-shift workers) may not be good candidates for orthokeratology. Meanwhile, we should also inform and educate patients who are sensitive to glare or halo about the potential adaptation with soft MF contact lenses and atropine. Otherwise, possible symptoms may outweigh clinical benefits.
Contrary to rapid progression in children and adolescents, the progression of adult-onset myopia in diopters generally acts less aggressively. However, due to a sustained period of axial elongation prior to adulthood, posterior choroid, sclera, and retina continuously experience physical stretching and insult, which may lead to more severe risks of myopic degeneration in young adults. Collectively, optical and pharmacologic approaches have shown to manage adult myopia effectively. Nevertheless, the absence of myopic degeneration does not necessarily indicate healthy, or ‘risk-free,’ retina. Practitioners should be prepared to step out of the ‘phoropter zone’ and familiarize with other clinical tools for myopia management. Axial length assessment at baseline and periodical intervals is highly recommended for determining prognosis and guiding treatment protocols. Furthermore, knowledge of macular and choroidal integrity found in OCT has shown promising application as potential biomarkers for myopia progression or development of myopia-related complications.
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- Fricke TR1, Jong M, Naidoo KS, Sankaridurg P, Naduvilath TJ, Ho SM, Wong TY, Resnikoff S. Global prevalence of visual impairment associated with myopic macular degeneration and temporal trends from 2000 through 2050: systematic review, meta-analysis and modelling. Br J Ophthalmol. 2018 Jul;102(7):855-862.
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