New research continues to evolve our understanding of treatment options for managing myopia progression. We are in the midst of a paradigm shift. Based on the clinical evidence that continues to build, eyecare providers are increasingly embracing the mentality of discussing myopia control options with their patients. While we still have a long way to go when it comes to fully understanding how best to manage myopia progression, we have multiple options that consistently show promise.
For many patients, the topic of treatment options that attempt to slow the progression of myopia as opposed to simply correcting it is a foreign one that has never been presented to them. Most parents are used to simply getting a new pair of glasses when their child’s myopia increases each year without giving it further thought. Despite there being no U.S. Food and Drug Administration (FDA)-approved or cleared options with a myopia control indication in the United States (all are off-label applications), practitioners are beginning to embrace myopia control in their practice. In Europe, there is a contact lens now approved with a myopia control indication.
As an eyecare community, the message that is frequently not discussed with patients is that even low amounts of myopia are associated with future ocular disease (Flitcroft, 2012); our lack of discussing this is likely because we previously had no alternate therapies for myopia. Given the increasing prevalence of myopia in the United States and worldwide (Vitale et al, 2009; Holden et al, 2016), should this still be the norm? A topic that I frequently hear discussed is whether it is time to start discussing potential treatment options with every patient so that they can make an informed decision when it comes to managing their myopia. Also, should that conversation happen as soon as they become myopic? I would argue that we owe it to our patients to present what is currently known (and what is still not known) based on the literature to allow patients and parents to be involved in the decision.
So, what are the options?
Studies of both orthokeratology (ortho-k) and center-distance soft multifocal lens designs have consistently reported treatment effects generally in the range of roughly 40% to 50% slowing of myopia progression during the first year or two of treatment (Huang et al, 2016). Thus far, only studies of center-distance multifocal designs have been reported; no clinical trials have investigated center-near designs.
That being said, most of these studies are either one or two years in length, with a few exceptions. It is important to recognize that extrapolating results beyond the period over which a study was conducted can lead to incorrect assumptions regarding sustained efficacy of a treatment. As we have seen with progressive addition spectacle lenses, it is not a given that a one-year treatment effect will be sustained over continued years of wear (Gwiazda et al, 2003). We still need confirmation of whether contact lenses for myopia control will have a continued treatment effect accrual over multiple years in a randomized clinical trial setting.
The Bifocal Lenses in Nearsighted Kids (BLINK) Study is an example of an ongoing clinical trial that seeks to answer the question of continued treatment effect accrual (Walline et al, 2017). The BLINK Study is a National Institutes of Health (NIH)-funded three-year clinical trial being conducted at the University of Houston and The Ohio State University. In this study, we are seeking to not only determine whether commercially available center-distance soft multifocal contact lenses are able to slow myopia progression over three years, we are also evaluating whether any treatment effect is dose dependent by including treatment arms with two different add powers versus a control arm wearing spherical soft contact lenses. Similar studies are either in progress or have concluded but have not yet published results in the peer-reviewed literature.
Such studies are delivering important information to eyecare providers. For example, the BLINK Study recently reported results on more than 300 children demonstrating that with an appropriate minus over-refraction to optimize vision, the +2.50D add multifocal contact lens being used in the study provides high-contrast acuity that is no different from spectacle correction while causing peripheral myopic retinal defocus (Berntsen et al, 2017). Studies such as this can help answer common clinical questions.
Hypothesized Mechanism of Optical Devices
Most optical devices such as ortho-k and multifocal (or bifocal) contact lens designs being investigated for myopia control are believed to cause a treatment effect by eliminating hyperopic retinal defocus in favor of myopic retinal defocus. We have solid evidence across multiple animal models that hyperopic retinal defocus (light focusing behind the retina) is an ocular growth signal, whereas myopic retinal defocus (light focused in front of the retina) is a very strong stop signal for eye growth (Smith, 2013).
We know that standard spectacle lenses increase peripheral hyperopic retinal defocus, with higher negative-power lenses causing greater increases in peripheral hyperopic defocus (Lin et al, 2010). For this reason, the majority of optical designs being evaluated to slow myopia progression are hypothesized to work by eliminating hyperopic defocus in favor of myopic defocus while still resulting in clear foveal vision. Evidence also exists in children showing that peripheral hyperopic retinal defocus experienced by the eye while wearing refractive correction is associated with faster myopia progression, whereas peripheral myopic retinal defocus is associated with slower myopia progression (Sankaridurg et al, 2011; Berntsen et al, 2013).
Atropine has also been studied as a myopia control agent. Though the mechanism of action is unclear, 1% atropine results in a treatment effect of roughly 77% over two years when considering the change in spherical equivalent refractive error (Chua et al, 2006). Lower doses of atropine, including 0.5% and 0.1%, can also slow the spherical equivalent change in refractive error by similar amounts (68% or more), and the lowest dose studied (0.01% atropine) slowed refractive error change by 59% over two years (Chia et al, 2012).
When considering whether there is a rebound effect (accelerated myopia progression after ceasing atropine), Chia et al (2014) found that higher concentrations had a greater rebound effect after stopping atropine compared to lower doses, with 0.01% atropine having the least amount of rebound. Given that low-dose atropine (0.01%) causes the smallest rebound when ceasing treatment and will also yield the most minimal effects on accommodation and pupil dilation, its use has become more popular.
However, while 0.01% atropine may slow the change in myopic refractive error by nearly 60% over two years, the data available on its effect on axial growth is not as convincing. When the axial length change of children using 0.01% atropine was compared to that of children using a placebo eyedrop from a previous study by the same research group, the axial growth of eyes in both groups was identical (Chia et al, 2012). This discrepancy between the influence of 0.01% atropine on the change in refractive error versus the change in axial elongation makes it unclear whether 0.01% atropine is accomplishing the ultimate goal of myopia control, which is to slow the eye growth that is associated with future pathology. At least one group plans to conduct a randomized clinical trial comparing both refractive error change and axial growth between children in a control group and children using 0.01% atropine.
That being said, a common question is whether combining pharmaceutical agents with optical devices will result in a greater treatment effect. A recent meeting abstract did report additional axial growth suppression after one year when 0.01% atropine was combined with ortho-k (Kinoshita et al, 2017). This suggests that there is a benefit to combination treatments, but more work is needed in this area. There is currently a study underway evaluating whether adding low-dose atropine (0.01%) with a soft multifocal lens yields a greater treatment effect.
Time to Change How We Talk to Patients
Recent myopia research has brought us a long way. While there are still many unanswered questions, options are available that have consistently demonstrated effectiveness in slowing progression. The question then becomes: How will you choose to discuss myopia the next time a child is in your examination chair? CLS
For references, please visit www.clspectrum.com/references and click on document #264.