Originally published: December 23, 2018
Updated: January 20, 2021
How can you tell if your myopia management strategy has been a success? Our popular Myopia Profile 'Managing Myopia Guidelines' infographics (free to download and available in eight languages) are designed to translate research into practice, and are a world first, evidence based clinical decision making tool designed to fill in a gap in the currently available resources. One of the key gaps in putting myopia management into practice is how to gauge success in your strategy. There are a few complicating factors in this.
To use the analogy of glaucoma again (for more, read the blog How myopic dioptres are like IOP), if an eye care practitioner is commencing topical glaucoma treatment, within a few weeks there is a clear indicator of whether the treatment has worked – is the IOP lower? There is some immediate feedback – but whether that IOP is low enough for that person or not is something which can only be established over time. In myopia management, we don’t have any immediate gauge of success, like a lower IOP, to be able to measure. We do need to ensure good acuity with our optical treatment, and ensure a minimal side effect profile with atropine treatment, but other than that, we similarly have to wait and see.
Axial length control?
Myopia control efficacy in research is gauged by both refractive and axial length measures. Most eye care practitioners don’t routinely measure axial length in clinical practice, mainly due to lack of access to the instrumentation and its expense. It is not only for this reason, though, that axial length (AXL) measurement is a bit of a problematic measure for gauging success in a clinical setting, although it is a definite necessity in a research setting. While a useful indicator of disease risk, we are still learning how to interpret AXL changes in the individual myope as an indicator of treatment success.
As lead author of the International Myopia Institute Clinical Management Guidelines, published in February 2019, our committee settled on including AXL measurement as a ‘standard procedure’ but with the caveat that there is currently no established criteria for normal or accelerated axial elongation in a given individual. You can read more about this in the blog entitled Axial length measurement – a clinical necessity?
The landscape on AXL now, almost two years later, is that percentile growth charts for children of Dutch and Chinese ethnicity have now been published, and novel measurement instruments are being released which incorporate axial length growth charts into their outputs. It could be that we end up utilizing growth charts like this on a percentile basis - we want to see myopes reduce in their percentile as an indicator of successful treatment - rather than aiming for a specific amount of mm/year reduction in growth. As our knowledge evolves on this, we'll likely have to update the Managing Myopia Guildelines Infographics - they're already on their fourth update in the first year of release!
If you're interested to read more on percentile AXL growth charts, this case study provides a useful reference table representing the 25th, 50th and 75th percentile values for AXL by age, gender and ethnicity. Used as an analogue reference chart, if you see your patient reduce from the 75th percentile value one year to the 50th percentile value the next year, as an example, that's treatment success.
So, we’re back to refractive progression, for which we have a published meta-analysis on typical single-vision distance corrected myopia progression in children, including Asian and non-Asian differences. The Myopia Profile 'Managing Myopia Guidelines' features a two-sided infographic to help you communicate to parents (the 'Protecting Children from Myopia' side) and for clinical management reference (the 'Myopia Management in Practice' side). The blog cover image above on Gauging Success is from the 'Myopia Management in Practice' side.
This small chart utilizes meta-analysis data to describe how much average progression could be expected, per year, for a child based on their age. It then applies a gauge of what constitutes 33% efficacy (an average of spectacle lens treatments and 0.025% atropine) and what constitutes 50% efficacy (an average of contact lens treatments and 0.05% atropine). The efficacy of atropine as monotherapy depends on its dosage – read more on our current knowledge on atropine concentration in Atropine – wonder or weak treatment?
The 'Managing Myopia Guidelines' solution
This infographic presents a world first solution to gauging success in myopia management - allowing you to address myopia progression as it occurs and set reasonable expectations for treatment.
A comparison is the BHVI Myopia Calculator, which projects progression from a minimum of age 6 up to age 17, and provides a long term illustration of treatments. This is very useful to demonstrate the concept of myopia progression to parents. When it comes to treatment efficacy, it does provide confidence intervals to allow for individual variation, but it is problematic projecting an average percentage efficacy over potentially 11 years of childhood, when most studies are 1-2 years in duration. It makes more sense to firstly prepare parents on their expectations of efficacy and then to address myopia progression as and when it occurs. The important message is that for younger children, a 50% efficacy means much more in absolute terms, when they are likely to progress more quickly, than for older children. If your 8 year old patient progresses -0.50D in a year, this likely constitutes a 50% myopia control effect, in comparison to the meta-analysis average. If your 12 year old patient progresses -0.50D in a year, though, this shows minimal efficacy and a new management strategy may be required. I have been doing these calculations in my head for many years, and using them in communication with parents - this infographic makes this process so much easier.
The hottest research off the press is that perhaps we’ll end up throwing percentage efficacy out the window, and settling instead on an absolute effect – more on that to come. Until we learn more, though, describing efficacy in view of measured, annualised refractive progression in your individual patient provides a short-term (1-2 year) evidence based approach, and provides ability to categorize treatments to facilitate selection and gauge success.
Interested in learning more?
Check out our online course Myopia Management in Practice. The course compiles all of the blog and learning content on the Myopia Profile website into a structured easy to follow format, that you can follow at your own pace. The course is free to access and includes MCQ questions and discussion forums to help solidify your learning.