There have been numerous advances made in the field of myopia management over the last 10 years, including the multifactorial nature of its development and progression and treatments to slow the progression of myopia, such as contact lenses and pharmaceuticals. However, many controversies associated with myopia management remain as well.

The Global Specialty Lens Symposium (GSLS) is focused exclusively on specialty contact lenses, and within that arena, myopia is a very hot topic. It’s also evident that eyecare practitioners (ECPs) are increasingly becoming involved with integrating myopia control methods into their practice. In fact, in a recent poll conducted by Contact Lens Spectrum, 42% of respondents indicated that they were actively practicing myopia control in their practice in 2019 (compared to 28% in 2018).^1,2 According to survey responses from the past two years, contact lenses dominate as the primary modality for myopia control, with about half of the patients being fit into overnight orthokeratology and half into peripheral-plus-power soft lenses for this purpose (Figure 1).^1,2 That said, pharmaceutical agents—either used alone or in combination with contact lenses—are gaining in popularity.

The interest that currently exists for myopia today is confirmed in the International Myopia Institute reports that were published in Investigative Ophthalmology & Visual Science in February 2019. This series of eight articles represents a consensus-based, peer-reviewed approach to looking at issues pertaining to myopia in general and specifically addresses classification, definition, epidemiology, interventions for myopia control, and study designs for myopia agents.

Another sign of myopia’s increased traction is the fact that the myopia initiative was named the Contact Lens Spectrum Event of the Year in both 2018 and 2019. And there has been much recent excitement, including the first contact lens to be approved for myopia control by the U.S. Food and Drug Administration (FDA).

In addition, a new meeting from Contact Lens Spectrum will debut in 2021 that reflects the need to have a meeting exclusively pertaining to myopia. The first annual Global Myopia Symposium (GMS) will be held immediately prior to the 2021 GSLS on Wednesday, Jan. 20, 2021. The Program Committee includes Drs. Kate Gifford, Lyndon Jones, Jason Nichols, Shalu Pal, and Jeff Walline.

At the recent GSLS, one of the general sessions addressed myopia in a debate format by a panel of experts that included Jason J. Nichols, OD, MPH, PhD (moderator); Mark Bullimore, MCOptom, PhD; Patrick Caroline; Donald O. Mutti, OD, PhD; Earl Smith, OD, PhD; Jeffrey J. Walline, OD, PhD; and James Wolffsohn, BSc(Optom), MBA, PhD. The following three controversial areas associated with myopia and its management were addressed:

1. The use of appropriate diagnostic and monitoring systems in clinical practice (notably axial length).
2. The primary mechanism of myopia development and management (peripheral refraction).
3. The contribution of optical design considerations of contact lenses with regard to myopia progression.

It’s important to add that the speakers were assigned a topic on which to present; they may—or may not—concur with the position that they were given to defend.

SHOULD WE BE MEASURING AXIAL LENGTH WHEN PRACTICING MYOPIA CONTROL?

Yes—James Wolffsohn, BSc(Optom), MBA, PhD To evaluate myopia progression, practitioners essentially have two areas to monitor—refractive error and axial length. To determine refractive error properly requires cycloplegia, which may not be accepted well by children. In addition, it is relatively subjective. Axial length, however, can be measured very accurately down to 0.01mm (0.03D) and, therefore, is a much more reliable method.

Changes in refractive error and axial length are not totally related. There can be reduction in the progression of myopic refractive error without concurrent reduction in the progression of axial length. Myopia-based retinal complications caused by stretching of the eye appear to be related to an increase in axial length, not to refractive error change. Therefore, to understand how to minimize vision-compromising effects of progressive myopia, practitioners have to first understand axial length.

So, what is the resistance to measuring axial length? From the practitioners’ standpoint, it can pertain to the need to have the appropriate instrumentation. Instrument costs can be prohibitive in some case, but the cost would be significantly less if more practitioners used it.

In summary, it is important to measure the parameter that we truly need and, as a profession, to step up and measure what really matters and what reduces the burden created by disease.

No—Jeffrey J. Walline, OD, PhD When the audience at this GSLS opening general session was polled, essentially everyone responded that they measure refractive error, but very few measure axial length. Refractive error and axial length are highly correlated, and most practitioners routinely measure refractive error. Why would another measure that is highly correlated to this be necessary?

For instance, let’s say you have a 9-year-old myope whom you diagnosed two years ago with a −1.50D refractive error and to whom you prescribed glasses. She returned a year later complaining of blurred vision, for which, of course, you performed a refraction revealing that her refractive error had progressed to −2.50D. You concluded that some form of myopia control was needed for this patient and prescribed center-distance soft multifocals. She returns this year, again complaining of distance blur, and you find that she has progressed −0.75D during that time.

Would measuring axial length help you decide whether you are slowing the progression or whether you may need to change the treatment? Because these two procedures are well correlated, it may not be worth the time and expense of performing a second procedure that adds difficulty for the patient and is not reimbursable. A good analogy is that you wouldn’t perform both non-contact tonometry and Goldmann tonometry on the same patient when these procedures are highly correlated.

DOES PERIPHERAL REFRACTION MATTER?

Yes—Earl Smith, OD, PhD Animal research has shown that refractive development is regulated by multiple independent mechanisms that are located in the retina and operate in a regionally selective manner. As a result, peripheral vision, peripheral signals, and peripheral refractive errors can affect eye shape and central refractive development independently of central vision. Practitioners know that visual signals from the fovea are not important for any aspects of vision-dependent growth that have ever been tested. When there are conflicting visual signals between central vision and the periphery, the periphery will dominate. For example, if we optically impose peripheral hyperopic defocus, this will produce central axial myopia. If we impose peripheral myopic defocus, we produce slower axial elongation in animals.

The good news for clinicians attempting to treat myopia is that optically imposed defocus in the periphery predictably alters refractive development in children just as it does with animals. Relative peripheral myopic defocus produced by progressive addition lenses, multifocal contact lenses, and orthokeratology have all been shown to reduce the progression of axial myopia in a clinically significant way.

On the opposite end, relative peripheral hyperopic defocus that is produced by center-distance multifocal contact lenses can accelerate axial growth in hyperopic children. So, as in animal models, imposed refractive errors can dominate central refractive development. Why have others not found this meaningful association between peripheral shape/peripheral refractive errors and progression in kids? First, it is difficult to characterize in a precise way the natural pattern of peripheral refractive errors. And progression rates—which are the usual outcome measure—are highly variable between individuals and are influenced by a number of different factors in addition to defocus.

Studies in humans have not necessarily considered the effects of correcting lenses; that is important because we know that negative spectacle lenses enhance peripheral hyperopia, and we need to take this into account when we study peripheral refractive errors. The ability of defocus to alter central refractive error decreases with eccentricity, and this is something that we need to examine more carefully to determine what amount of eccentricity is most important. Many studies have looked at eccentricities that are probably too extreme. We have found that anything outside of 20º to 25º is beyond the zone that influences central refractive error. And, some methods for assessing ocular shape and peripheral refraction may not be appropriate or sufficiently sensitive. For example, with spectral domain OCT (SD-OCT), practitioners can see differences in shape between myopic and non-myopic eyes at about 5º. Auto-refraction and other measures of refractive error are very inaccurate at those short eccentricities, especially if there are large changes in refractive error.

So, while studies have not reported results that would support the idea that peripheral refractive error is important in normal myopia development, there is a long way to go to rule out the fact the peripheral refraction is not important.

No—Donald Mutti, OD, PhD There is much validity to what Earl Smith has found with his research. Imposed peripheral myopic defocus will slow the growth of the eye and will slow myopia progression. That has been shown with animal models as well as with children. It can be argued that we are measuring the right thing when we ask “Does peripheral hyperopic defocus influence eye growth because we are measuring peripheral defocus?”

It is being measured with an auto-refractor, which is not completely precise. However, if you measure several hundred children across numerous studies, practitioners can obtain a reasonable degree of precision. Do we have the right mechanism for peripheral defocus? Getting the mechanism right is important for evidence-based practice. The mechanism is supposedly that peripheral myopic defocus with a myopia control treatment is counteracting the negative effects of peripheral hyperopic defocus. Therefore, the concern is that if peripheral hyperopic defocus is the problem, why don’t we see stronger effects in human patient-based studies?

In the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) study, the effect of having an extra diopter of relative peripheral hyperopia when observing subjects becoming more myopic was essentially non-existent.³ There was essentially no increased risk from that. In fact, several studies have concluded that peripheral hyperopic defocus is not associated with becoming myopic.^4-6

With regard to rate of myopia progression, the CLEERE study reported only 0.02D of additional myopia progression per diopter of hyperopic defocus. In other words, it was not very significant. More so, we would predict that axial length would be affected, and again, it was not impacted.³

Peripheral refractive data can be difficult to analyze, and the results can be variable. If you perform it carefully and concentrate on central axial length, you will not find an association. Therefore, we need to rethink our assumptions about mechanism and perhaps think about why are we really obtaining effects with peripheral myopic defocus.

DOES THE OPTICAL PROFILE OF SINGLE-VISION LENSES CONTRIBUTE TO MYOPIA PROGRESSION?

Yes—Patrick Caroline The interest that my research group had in this topic originated from Brien Holden’s presentation six years ago at [GSLS] when he commented that single-vision, minus-power soft lenses increase in minus power from center to periphery. We followed up with this in our laboratory using the Rotlex Class Plus lens analyzer and found a very similar effect. Standard daily disposable minus-power soft lenses do increase in power from center to periphery.⁷

There are two techniques for assessing this. The standard uses Hart-Shackman, and a more advanced method uses spot analysis for measuring the optics of soft contact lenses. With this method, our research team assessed all 12 currently available daily disposable soft lenses, each in a −3.00D power. We found an increase in minus power in the periphery of these lenses typically in the amount of only 0.25D to 0.37D. The exception was the MiSight lens (CooperVision), recently approved by the FDA for myopia control, which shows an increase in plus power toward the periphery.

When evaluating daily disposable lenses in a −6.00D power, the amount of increase in minus power in the lens periphery is greater. These findings have significant implications.

If you are performing a study on myopia control, it is important to know the optical profile of the lens and, in particular, to utilize a lens that does not increase in minus power toward the periphery. Likewise, for presbyopic patients and notably for emerging presbyopes, wearing a lens that increases in minus power toward the periphery can compromise the vision that they achieve at near.

This is an indication that manufacturers need to be conscientious of the optics that are being placed on the anterior surface of these lenses. In light of everything that we know about myopia control, we need to be provided with flat optical profiles on our contact lenses.

No—Mark Bullimore, MCOptom, PhD The most important factor in addressing this issue is, of course, a randomized clinical trial. Walline et al randomized 500 children into spherical soft lenses or spectacles and followed them for three years and found no difference in their progression of refractive error.⁸ Soft lenses do affect peripheral refractive error, but they move them in the myopic direction. In uncorrected myopes, there is actually a small hyperopic error in the periphery, as myopic eyes become longer but do not grow so much equatorially.

However, if you place a soft lens on the eye, there is more peripheral myopia and, therefore, less—not more—minus power being placed in the periphery, as these measurements are made in the peripheral eye. Moore et al found this same result, with an increase in peripheral myopia resulting in less minus power being exposed to the peripheral retina.⁹ Spectacle lenses do produce peripheral hyperopia and, therefore, are worse compared to spherical soft lenses as it pertains to myopia progression.

With regard to the data presented by Patrick Caroline, the measurement techniques used are designed to measure paraxial power—the power parallel to the optical axis, with rays that end up near the fovea and not on the peripheral retina. For spectacle lenses, which these instruments are designed to measure, that is not a problem.

With a contact lens, however, at a chord length of 3mm, light strikes the surface at a very oblique angle. That results in a flawed measurement. Tilting a lens induces spherical and cylindrical power in the direction of the power of the lens. This induced power can be calculated. For example, if you tilt the lens 34º, your measured spherical equivalent would be much more minus in power. Yes, you can measure more minus power, but it has no effect on what the peripheral retina is receiving and has no effect on myopia progression.

SUMMARY

A number of questions remain as to how myopia progression can be controlled. These and related topics will be the focus of the Global Myopia Symposium in January 2021. We hope to see you there. CLS

REFERENCES

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3. Mutti DO, Sinnott LT, Mitchell L, et al; CLEERE Study Group. Relative peripheral refractive error and risk of onset and progression of myopia in children. Invest Ophthalmol Vis Sci. 2011 Jan;52:199-205.
4. Atchison DA, Li S-M, Li H, et al. Relative peripheral hyperopia does not predict development and progression of myopia in children. Invest Ophthalmol Vis Sci. 2015 Sep;56:6162-6170.
5. Sng CCA, Kin X-Y, Gazzard G, et al. Peripheral refraction and refractive error in Singapore Chinese children. Invest Ophthalmol Vis Sci. 2011;52:1181-1190.
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8. Walline JJ, Jones LA, Sinnott L, et al; ACHIEVE Study Group. A randomized trial of the effect of soft contact lenses on myopia progression in children. Invest Ophthalmol Vis Sci. 2008;49:4702-4706.
9. Moore KE, Benoit JS, Berntsen DA. Spherical Soft Contact Lens Designs and Peripheral Defocus in Myopic Eyes. Optom Vis Sci. 2017 Mar;94:370-379.