Myopia control isn’t rocket science; every OD who reads this has the clinical skills and education to not only correct myopia but to apply the latest science to help patients manage progression of myopia. Care of myopic patients is Optometry’s core competence and as the standards change from just being able to correct myopia to being able to influence the progression it’s vital we own the methods behind myopia control, practice them and educate our patients on our abilities to do so. Arguably managing myopia is quickly becoming the standard of care; not just correcting it through standard methods.
The general public has no idea what we are capable of in terms of managing the condition as they are conditioned to expect children’s vision to change regularly and the research and science are relatively new and poorly disseminated to the general public. Many optometrists avoid practicing myopia control and continue to prescribe as trained, but this is creating an opportunity for non-optometrists and corporations to get involved in the care of myopes. It is possible that by not implementing myopia control we are opening a window for others to take away our practice of refractive eye care.
Entrepreneurs have formed companies to extract this resource from us and profit from it. They can only be successful if we willingly hand this over to them by referring to them and supporting them. Myopia control is a severely unmet medical need in communities, is greatly appreciated by concerned parents, helps reduce risk of eye disease later in life for the patient, is not covered by vision insurance and is very profitable. This is a high-level overview of methods used and science behind myopia control for our practices.
Science Behind Myopia Control
Correcting myopia involves moving light that focuses in front of the back of the eye to the back of the eye. Due to the eyes curvature, single vision lenses used to correct myopia cause light that falls outside of the foveal region to focus at a virtual point behind the eye peripheral to the foveal region. It is believed that the mechanisms for eye growth exist in this region, and that the light that is refracted “behind” the eye to the virtual focus is a stimulus for the eye to “chase” the light by growing towards the virtual peripheral focus. The virtual peripheral focus that ends up behind the eye is called “hyperopic defocus”. Every single vision lens prescribed to neutralize refractive error creates a peripheral hyperopic defocus when prescribed for emmetropia at the fovea, and thus is a stimulus for growth in axial length. In other words while we have been correcting myopes we have also been unwittingly causing progressive myopia at the same time. We stimulate myopic creep just by correcting it by creating hyperopic defocus. Of course historically we’ve had minimal understanding of this and no tools to adjust the peripheral focus “inwards”. The ability to do so, to create a ‘myopic defocus” where direct light falls on the fovea and peripheral light bends “inward” into the eye is a relatively recent advancement, achieved by either “molding” the central few millimeters of the cornea while keeping the peripheral optics of the cornea from creating peripheral hyperopia as we do with Orthok, or using distance center multifocal soft contact lenses to achieve a similar peripheral myopic defocus effect.
Scientists believe Atropine has some effect on the growth mechanisms located in the mid-periphery of the back of the eye but there are many studies that need to be done to elucidate the exact reason it works. The mechanism of action of Atropine is still debated, but it apparently has not much to do with its effect on the accommodative system. Recent studies show that Atropine in combination with creating peripheral myopic defocus may be even more effective in managing myopic creep.
Methods of Myopia Control
Three methods of myopia control have been identified that are supported by peer-reviewed research. These methods are Atropine .01%, Orthokeratology and Distance-Center Multifocal Soft contact lenses. How we manage patients using these methods varies per clinician, but not greatly.
There are many resources that can help a practice get started with Orthokeratology for myopia control. The equipment you need you likely already have, as long as you have standard exam lane equipment and a topographer. It’s great to set up a relationship with an experienced RGP lab and use the lens consultants to guide you through your first few fits. Understanding how to document patient education regarding risks of Orthok and emphasizing cleaning and care regimens are an important part of the total care of the Orthokeratology patient. The best resource, in my opinion, is the American Academy of Orthokeratology and Myopia Control website and their annual convention is the best place to get the basics you need to start fitting Orthokeratology. Remember, pupil size is critical. If the pupil is smaller than the zone providing the peripheral myopic defocus OrthoK may not be the best method of providing myopia control even though it corrects the child’s myopia.
Distance Center Multifocal Soft Contact Lenses
Fitting distance center multifocal soft contact lenses on children and adolescents creates a myopic defocus similar to Orthok but without the molding that takes place with Orthok. Fit the lenses to emmetropia. If the lens you use has an add, like the CooperVision center distance multifocal pick the highest add. If you use the Naturalvue multifocal it is a standard add across all powers so you don’t need to calculate what add to use. We see our patients in their first year every 3 months for an A-scan to watch for any axial length changes. If we see axial length changes we might add atropine as an adjunct. There are other distance center lenses; Synergeyes recently released a distance center multifocal as well.
Atropine has been shown to have an effect in many studies, and different concentrations have shown different effects, but .01% Atropine has been shown to be effective with an ability to limit side effects of this medication for children. .01% Atropine has no effect on a child’s daytime vision but if Atropine is the only thing prescribed for myopia control the child still must wear eyeglasses to see during the day, unlike with Orthok or distance center multifocal soft contact lenses. There will still be hyperopic defocus, which is why I feel standard of care is shifting towards using two methods for children, either Orthok or distance center soft multifocal lenses WITH atropine as an adjunct. There are many sources of Atropine parents can order their medication from so once the prescription is provided you may choose to follow the child as you deem appropriate.
Gauging success or failure
Historically the standard we use to discuss success or failure of patients who we practice myopia control on has been limiting change to .50D per year change or less. Our standard for measurement and comparison has been refractive data. Most experts now agree a more accurate picture of myopic change is by comparing the change in axial length, achieved by A-scan along with refractive data. We are not too far off from a time where the change in axial length is the gold standard for success or failure of myopia control methods. There is also no uniform standard we use to discuss the success or failure of our efforts with patients, so it’s likely we each have our own standards, even though this is unscientific. In my practice we refract, measure axial length with an IOL master and discuss both data points with patients, educating them about what each data point means in terms of the progression of their child’s myopia or lack thereof. For new myopia control patients, we refract and measure axial length on a quarterly basis – if success is achieved in the second year we watch bi-annually. As most parents are familiar with units of change we use in quarter diopter steps (from reading their child’s glasses Rx year after year) the standard I have adopted for success in terms of axial length change is .03mm per year or less, which I consider a “halting” of progression, .06mm or less is a major reduction in the rate of the myopic change and I still set .50D change as standard change for these children, a relatively high bar. The .03mm number is used because it is less than .12 D per year and is also at the high end of the statistical margin of error we can expect from an A-scan. When we achieve success in terms of full stabilization by my definition I am able to tell parents we succeeded in reducing myopic creep by a “factor” that is determined by taking the average rate of change over the past year to 3 years and dividing it by the dioptric equivalent. For example, if we measure .02 mm change in axial length on a child who’s average change was 1D over the past 3 years I’ll divide 1D by .06D (.02 mm axial length increase) based on the formula below and tell the parents we reduced the myopic creep by a factor of 17X. This figure is easily understood by parents and helps us gauge our success as clinicians. I think it is important vision scientist’s work towards standardizing these numbers. I am providing this simple chart for you to use to measure and gauge myopia control success when discussing with parents.
Axial Length Delta for Myopia Control Patients
Based on 1mm Axial Length Change = 3D Myopic Shift
So .33 mm Change per Diopter increase in myopic creep equals
.08 mm per .25 D
.04 mm per .12D
Building and Marketing Your Myopia Control Specialty
There are many resources that exist within your practice to build this specialty; first and foremost is your existing patient base. Let your patients know you can help manage myopic creep by sending out customer communications. Host seminars in your office and to community groups. Get involved with local youth organizations to tell your story. Ask the patients who have benefitted from myopia control to refer friends and family and perhaps have a referral incentive. Consider registering at MyopiaInstitute.com, a site I designed to drive your listing for myopia control and other google keywords to the top of page 1 on Google in your region within 3 months of signing up.
Optometry is uniquely positioned to care for the myopic patient; there is no other profession that is so highly trained to treat and manage this condition. As the standard of care for management changes, be sure to stay on top of it. It benefits your patients, your practice and your profession.