Myopia Control Today
Myopia Control Today
A look at the prescribing options available to reduce the progression of myopia in children.
By Katherine M. Bickle, OD, MS, & Jason J. Nichols, OD, MPH, PhD, FAAO
Nearly 42% of the U.S. population (in the 12- to 54-year-old age range) are myopic (Vitale et al, 2009). This percentage has increased dramatically since the 1970s when only 25% of those 12- to 54-year-olds were myopic. Not only has the percentage of those who have myopia increased, but the refractive error of myopic patients has also increased substantially (Vitale et al, 2009) (Table 1).
TABLE 1 Comparison of the percentage of myopic individuals in the United States from 1971 to 1972 and from 1994 to 2004 as reported by Vitale et al (2009)
||1971 to 1972
||1994 to 2004
||Myopic individuals in the United States
||< −2.00D myopia
||−2.00D to −7.90D myopia
||> −7.90D myopia
We see this trend in our practice setting, so how can we expand upon current prescribing patterns to reduce the progression of myopia in children?
On average, children in the United States progress 0.50D/year (Braun et al, 1996; Gwiazda et al, 2003) until reaching a final myopic refractive error in their teenage years (Goss, 1987). While there are patients who progress or become myopic in their 20s or later, myopia control studies have focused on children who become myopic not as a result of ocular pathology.
Myopia increases a patient’s risk for glaucoma, retinal holes and tears, retinal and vitreal detachments, cataracts, lattice degeneration, lacquer cracks, and myopic macular degeneration (Wong et al, 2003; The Eye Disease Case-Control Study Group, 1993; Younan et al, 2002; Pierro et al, 1992). Potential ocular complications associated with myopia and a significant increase in the percentage of individuals who are myopic have contributed to the expansion of myopia control research, with the ultimate goal being to translate this to the clinical setting. This interest has also expanded to parents who have investigated options or inquired with their eyecare practitioner about ways to slow their child’s myopia progression.
Myopia Control Options Studied
Previous studies have investigated atropine (Yen et al, 1989; Shih et al, 1999; Chua et al, 2006; Wu et al, 2011; and others. Full list available at www.clspectrum.com/references.), pirenzepine (Tan et al, 2005; Siatkowski et al, 2008), soft multifocal contact lenses (Sankaridurg et al, 2011; Anstice and Phillips, 2011; Walline, Grenier et al, 2013), corneal reshaping lenses (Cho et al, 2005; Walline et al, 2009; Cho and Cheung, 2012), alignment-fitted GP lenses (Katz et al, 2003; Walline et al, 2004), bifocal or multifocal spectacles (Fulk et al, 2000; Gwiazda et al, 2003; Edwards et al, 2002), and undercorrection (Adler and Millodot, 2006; Chung et al, 2002) as potential options for myopia control. All of these methods, excluding alignment GP lenses and undercorrection, have shown varying amounts of success in clinical trials of reducing the progression of myopia compared to a control group.
Although debatable, most would likely agree that at least a 50% reduction in myopia progression is a clinically significant one. With methods that result in a lower percentage, practitioners may be hesitant of the impact on children’s vision, overall satisfaction, or other side effects with the treatment option. Thus, when considering the risk-versus-benefit ratio, we are able to assess and determine the best overall treatment options for our patients.
Atropine While atropine has shown to be the most effective option after one year of treatment (76% to 96% reduction in myopia progression), there are potential ocular (paralysis of accommodation and fixed mydriatic pupils) and systemic (decreased lacrimation, allergic reaction, tachycardia, restlessness, and dryness of the mouth, throat, and skin) side effects (North and Kelly, 1987). However, more recent research indicates that lower concentrations of atropine (0.01%) may be effective in reducing the progression of myopia while reducing ocular side effects (Chia et al, 2012).
Despite this, atropine is prescribed much less frequently in the United States than in certain areas of Asia (Fang et al, 2013), and it has not been approved by the U. S. Food and Drug Administration (FDA) for myopia control.
Pirenzepine Pirenzepine results in similar ocular side effects observed with atropine (Ostrin et al, 2004) and also has not been approved by the FDA for myopia control. Additionally, it has been shown to be less effective compared to atropine and isn’t routinely prescribed in the United States (Tan et al, 2005; Siatkowski et al, 2008).
Undercorrection and Alignment-Fitted GPs Two methods tested, undercorrection and alignment-fitted GP lenses, have not shown to reduce the amount of myopia progression when compared to control subjects (Adler and Millodot, 2006; Chung et al, 2002; Katz et al, 2003; Walline et al, 2004). Thus, these options aren’t recommended for myopia control. This is especially important to remember as you may have encountered parents who are concerned that strengthening their child’s prescription will further increase their refractive error.
Bifocal and Multifocal Spectacles Although studies evaluating bifocal or multifocal spectacles have shown a positive treatment effect, the reduction in myopia progression is significantly less than that observed with soft multifocal contact lenses or corneal reshaping lenses (Gwiazda et al, 2003; Walline, Greiner et al, 2013; Cho and Cheung, 2012). Therefore, this option is typically reserved for patients who are unable or unwilling to wear contact lenses.
Myopia Control Trials with Contact Lenses
Currently, the best options we can provide to our patients when factoring in the potential impact on myopia progression are center-distance soft multifocal contact lenses and corneal reshaping lenses (orthokeratology). Studies evaluating children in soft multifocal contact lenses have found a 34% to 79% reduction in myopia progression (Figure 1) compared to control subjects, while studies involving corneal reshaping contact lenses have found a 32% to 62% reduction (Figure 2).
Figure 1. Soft multifocal contact lens studies.
Figure 2. Corneal reshaping lens studies.
What mechanism is involved to make these lenses effective? Despite initial assumptions that the fovea was a contributing factor in determining axial elongation, studies testing the refractive error of monkeys after various treatments have concluded that the peripheral retina plays an important role in refractive error development (Smith et al, 2009). Peripheral myopic defocus has been shown to slow axial elongation, whereas the opposite occurs with hyperopic defocus in the periphery (Liu and Wildsoet, 2012; Smith et al, 2009).
When a patient wears single-vision spectacles or contact lenses, central light rays focus on the retina while peripheral light rays focus behind the retina, creating a peripheral hyperopic defocus. In comparison, when a child wears center-distance soft multifocal lenses or corneal reshaping lenses, central light rays still focus on the retina to provide a clear image while there is peripheral myopic defocus from peripheral light rays (Figure 3).
Figure 3. The top image (A) shows the focusing of light rays in a patient fit with single-vision spectacles or soft contact lenses while the bottom image (B) represents the focusing of light rays in a patient fit with center-distance designed soft multifocal contact lenses or corneal reshaping lenses.
Walline, Greiner et al (2013) conducted a two-year study to evaluate the myopia progression and axial elongation in 8- to 11-year-old subjects fit into a center-distance soft multifocal contact lens with a +2.00D add. The control group consisted of subjects fit in single-vision contact lenses from a previous study. Axial elongation for the soft multifocal contact lens wearers and the single vision contact lens wearers was 0.29mm ± 0.03mm and 0.41mm ± 0.03mm, respectively, while the amount of myopia progression was –1.03D ± 0.06D and –0.51D ± 0.06D, respectively.
Similar treatment effects were observed in a study evaluating orthokeratology. In a two-year randomized clinical trial, subjects were fit in either orthokeratology lenses or single-vision spectacles, respectively (Cho and Cheung, 2012). After two years, axial elongation was 0.36mm ± 0.24mm and 0.63mm ± 0.26mm in the orthokeratology and single-vision spectacle groups, respectively.
Additionally, a greater percentage of younger children (7 to 8 years old) in both the orthokeratology (20%) and control (65%) groups had myopia progression >1.00D/year compared to the older children, 9% and 13%, respectively (Cho and Cheung, 2012). This suggests that because younger children are more likely to progress more quickly, it may be beneficial to consider myopia control options at a younger age.
While several studies have examined fitting spherical contact lenses, a commonly asked question by practitioners is how to manage our patients who have higher amounts of astigmatism. One two-year study evaluated this by fitting children who have –1.25D to –3.50D of with-the-rule astigmatism in either toric orthokeratology lenses or single-vision spectacles (Chen et al, 2013). After two years, the subjects wearing the toric orthokeratology lenses had a 52% reduction in axial elongation compared to those fit in single-vision spectacles. Practitioners should consider that these fits may be more complicated, but it is promising that we have a myopia control option for our patients who have moderate amounts of astigmatism.
Contact Lens Options and Visual Performance Considerations
A number of manufacturers make center-distance contact lenses. Some also allow you to specify certain contact lens parameters including the add power. Being able to specify add powers up to +4.00D could be beneficial as it is theorized that higher add powers will result in a greater treatment effect, although this has not been scientifically confirmed. However, not every child may tolerate a +4.00D add multifocal; thus, it is important to choose the most appropriate add for each child.
We usually start by fitting patients into the maximum add power that they can tolerate, subjectively and objectively, and carefully confirm this through our clinical testing before dispensing. If you have fit these lenses in presbyopic patients, use your clinical expertise to assist you while addressing your pediatric patients’ needs. A child fit with this lens type may experience the same visual problems as a presbyope would, but the child may not be able to describe these symptoms.
One study enrolled 24 myopic adults to compare the visual performance of two different multifocal lenses and the subjects’ habitual correction (Kollbaum et al, 2013). While no differences were reported in high-illumination/high-contrast distance visual acuity, there was a reduction in visual acuity with testing at low-illumination/low-contrast with both multifocal lenses compared to with habitual correction. Additionally, subjects gave worse ratings for ghosting and average visual quality with both multifocal lenses compared to with their habitual correction.
These symptoms may have been easier for these subjects to report compared to children, as these subjects were adults who had worn correction for more years compared to a younger pediatric population. Thus, it is important to discuss these potential visual limitations with your patients and their parents.
While troubleshooting with pediatric patients, asking specific questions related to glare, ghosting of images, vision during certain tasks, etc., can be extremely beneficial. Having images in your office that show examples of common symptoms can be helpful to these patients who may not otherwise understand certain terminology. Some children may be better able to communicate symptoms through a questionnaire.
Comparing low-contrast visual acuity and contrast sensitivity with habitual correction and the multifocal lenses may also help you identify potential issues. Additionally, a child who is symptomatic may have a decentered lens, perform activities that require optimal vision, or is a critical observer.
One study evaluated vision-related quality-of-life measures in children (ages 6 to 12 years old) fit into orthokeratology contact lenses or single-vision spectacles (Santodomingo-Rubido et al, 2013). The children fit in orthokeratology contact lenses reported better overall vision, appearance, satisfaction, academic performance, and peer perceptions compared to the children fit into spectacles. These results are encouraging and can be a motivating factor to both patients and parents when fitting children in this form of correction.
Soft Multifocal Versus Corneal Reshaping Lenses
You may find that a child is a good candidate for both soft multifocal and corneal reshaping lens options, so it is beneficial to understand the parents’ preferences. What visual demands does the child have while at school or during extracurricular activities? Do the parents feel comfortable with the child wearing a contact lens overnight? Or, would they prefer to not have to worry about the child having issues at school or at other activities while wearing lenses during the day? You may have fit that child’s parent(s) in contact lenses, and now those parents feel more comfortable fitting their children in the same type of lenses because they know what to expect.
If the patient is a current contact lens wearer, switching to another soft contact lens material should present no issues. But studies evaluating the risk of microbial keratitis when switching a patient from daily wear soft contact lenses to corneal reshaping lenses are needed.
It is important to discuss the risks associated with contact lens wear during your conversation with patients and their parents along with alerting them of symptoms suggestive of an infection. Parents are less apprehensive if they know what is normal and what isn’t during the adaptation and daily wear of contact lenses.
Patients who have higher refractive errors and are fit in corneal reshaping lenses have shown less increase in vitreous chamber depth compared to those of lower refractive errors, potentially indicating that corneal reshaping lenses may be more beneficial to those children who have higher refractive errors (Cho et al, 2005).
However, corneal reshaping lenses are not routinely fit on patients who have significant refractive errors (> –6.00D) as they cannot fully correct that magnitude of refractive error. One study, however, showed a 63% reduction in axial elongation when correcting 4.00D of subjects’ myopia (initial myopia of at least –5.00D) and prescribing spectacles to correct for any residual refractive error compared to the control group (Charm and Cho, 2013).
Implementing Myopia Control in Your Practice
How do we introduce our patients and their parents to this concept? How do we balance the discussion of the impact of factors such as glare, halos, and overall quality of vision with the potential to slow down myopia progression? Staff members are valuable resources to your practice. They can easily begin this conversation as they most likely interact with patients first.
While trying to maximize your time with each patient, it is helpful to keep presentations simple and concise. Explain to parents that two of the best contact lens options for their child are myopia control or daily disposable lenses, which result in increased convenience and compliance (Dumbleton et al, 2009). Parents appreciate this simplicity. Additionally, you may find that parents arrive for appointments having already developed opinions on different forms of correction based upon their own previous experience, word-of-mouth, researching options on the Internet, etc.
Depending on your practice setting, you may not routinely examine children. However, even if you don’t, your patients may have children or other relatives who could benefit from your knowledge of the available myopia control options. The resulting contact lens professional fees and materials are not only financially rewarding for your practice, but you now have loyal patients.
Because no current options are cleared by the FDA for myopia control, practices that fit contact lenses for myopia control should use informed consent documents. This provides you with the opportunity to educate patients and parents on the available options and that contact lenses used for myopia control are all off-label.
Particularly with those parents who were not aware of these options, discussing results of previous studies can help them understand the potential with these options. While several studies have shown that there are benefits with the treatments mentioned above, not every child will respond the same way. Some children may have the same amount of myopia progression while wearing or not wearing a contact lens for myopia control. In addition, while fitting patients in these options, we have no way of knowing what that child’s refractive error would be had we not intervened.
You may have a certain age or certain characteristics (maturity, dexterity, and/or motivation) that you consider when deciding to fit a child in contact lenses. Children as young as 8 years old have been shown to be successful contact lens wearers (Walline, Gaume et al, 2007). Children of a younger age (6 to 7 years old) progress more quickly compared to older children (11 years old) (Hyman et al, 2005).
Thus, choosing to fit a child in a corneal reshaping lens or soft multifocal lens at a younger age may be advantageous from that standpoint. Previous results indicate that the fitting time for children and teenagers is similar, while it takes approximately 11 minutes more for children to perform application and removal training compared to teenagers (Walline, Jones et al, 2007).
Studies have also evaluated overall quality-of-life measures and ocular health in children and teenagers fit in soft contact lenses compared to those wearing spectacles. Appearance, recreational activities, and satisfaction with correction were the most significant improvements observed while wearing soft contact lenses compared to spectacles (Rah et al, 2010). When considering differences in ocular health between current patients who were fit as children to those fit as teenagers, there were no differences in biomicroscopy signs or prior history of contact lens-related complications between the groups, indicating that being fit as a child did not increase contact lens-related complications (Walline, Lorenz et al, 2013).
Parent Perspectives on Myopia Control
When discussing different treatment options with patients and parents, it is important to understand the knowledge of—and opinions toward—the different options. In Hong Kong, one study found that 86% of parents were aware of orthokeratology as an option for myopia control while only 29% were of soft contact lenses (Cheung et al, 2014). Approximately 52% of parents became aware of these options through word-of-mouth, while 35% of parents were informed of the options by a medical care provider.
Additionally, parents who would prefer to have their child in contact lenses compared to spectacles rated convenience as a higher priority compared to safety; the opposite was observed with those parents who preferred spectacles. Interestingly, only 15% of parents reported that contact lenses were an acceptable option for vision correction in children 8 to 11 years old.
What happens after the correction for myopia control is removed? Does the same reduction in myopia progression that has been reported after one year occur after five or 10 years? New, longer randomized prospective clinical trials will help answer these questions. More lens options for patients would also be beneficial, as would understanding the potential benefit of other current commercially available contact lenses of differing multifocal designs.
Understanding that reducing a child’s final myopic state may also decrease that child’s risk for ocular complications as a result of being myopic is also essential. While there are many unanswered questions, we have made substantial progress with myopia control research. We experience this when parents come to our office asking about such options for their child before we can even begin the conversation. CLS
For references, please visit www.clspectrum.com/references and click on document #225.
Dr. Bickle is a PhD student at The Ohio State University College of Optometry and is in private practice in Granville, OH.
Dr. Nichols is the Kevin McDaid Vision Source Professor at the University of Houston College of Optometry as well as editor-in-chief of Contact Lens Spectrum and editor of the weekly email newsletter Contact Lenses Today. He has received research funding or lecture honoraria from Vistakon, Alcon, and Allergan.
Contact Lens Spectrum, Volume: 29 , Issue: August 2014, page(s): 20, 21, 23-26