May 24, 2019
By Kate Gifford, BOptom, PhD, FAAO
How can you tell if your myopia management strategy has been a success? Our new infographic Which option to slow myopia? is designed to translate research into practice, and is 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, AXL measurement is currently an uncertain diagnostic criteria for the individual myope. As lead author of the International Myopia Institute Clinical Management Guidelines, 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?
So, we’re back to refractive progression, for which we have a published meta-analysis, including Asian and Caucasian differences.1 The ‘Which option to slow myopia?’ infographic features a small chart which utilizes this 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 what constitutes 50% efficacy (an average of contact lens treatments). The efficacy of atropine as monotherapy depends on its dosage – read more in Atropine – wonder or weak treatment?
The ‘Which option to slow myopia?’ solution
This infographic presents a world first solution to gauging success in myopia management. The BHVI Myopia Calculator projects progression from a minimum of age 6 up to age 17, and provides a long term illustration of treatments, and while it does provide confidence intervals, it is problematic projecting an average percentage efficacy over potentially 11 years 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. We’re thrilled to now be able to share this simplified, accessible information with you to help you do the same.
The hottest research off the press (or not even in press yet!) 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 is our best evidence based approach.
1. Donovan L, Sankaridurg P, Ho A et al. Myopia progression rates in urban children wearing single-vision spectacles. Optom Vis Sci. 2012;89:27-32.