New research out of the 2024 American Academy of Optometry (AAO) annual meeting this week sought to understand two broad areas of myopia progression that are often questioned—yet still not properly understood among clinicians.
These latest findings were presented by Mark Bullimore, MCOptom, PhD, FAAO, during the AAO’s scientific poster session on Thursday, Nov. 7.
Give me some background first.
The prevalence of myopia has been a growing cause of concern in recent years.
In fact, uncorrected myopia is already considered a leading cause of distance vision impairment across the globe.
- Case in point: An estimated 30% of the world’s population is currently myopic—and by 2050, that prevalence is expected to escalate to 50%.
And in just the United States, myopia has been recorded with a prevalence of 42%—nearly doubling in just the last 30 years.
However: As we’ve previously reported, a number of myopia-focused initiatives, coalitions, digital resources, and research reported just in the last few years have all targeted the collective goal of managing and treating this pediatric-centric, preventable disease.
Now to this research at hand: What were these two areas of focus?
Dr. Bullimore noted two key questions he and his co-authors Noel Brennon, Xu Cheng, and Monica Jong were looking to answer:
- What does average myopia progression look like?
- How should myopia control be interpreted?
And how did they investigate this?
Through an “omnibus model,” according to Dr. Bullimore.
What this is: A type of statistical test that explains whether the variance in a particular data set is significantly greater overall than an unexplained variance.
- And in this case: “This model brings together several of our key findings from the past few years of research while also making a few projections,” he told Glance.
Ah, I see. So what’s first?
Answering that initial question: What is an average (normal) progression of myopia in a pediatric patient?
Dr. Bullimore noted two important factors that play a role in determining this:
- Age
- Race/ethnicity
“The younger a child is (myopic or not), the more rapidly their myopia is going to increase,” he said. “So the axial elongation (AE) of an 8-year-old’s myopia will, on average, increase about twice as much—or twice as fast—as a 13-year-old.”
That translates to a slowing in progression of roughly 15% per year, according to Dr. Bullimore.
- Along these lines: The research also noted an apparent 15% reduction per (year) in (AE) in treated myopes—beyond the first year of treatment.
Why this matters: This data only further stresses the importance of initiating early treatment.
And that second factor?
Pediatric patients in East Asia (i.e., Japan, China, Hong Kong, Korea, etc.) typically progress in myopia an estimated 40% faster than other pediatric groups, specifically in North America, according to Dr. Bullimore.
“Whether that’s a genetic or environmental-based influence, we tend to favor the environment argument,” he said, “and that has to do with the more intense education in that part (East Asia) of the world—the cultural component for those differences.”
Gotcha. Now move on to the role of efficacy for myopia control treatment.
“While it's been popular to talk about percentage slowing or percentage efficacy, we don't believe that's a good metric to use,” Dr. Bullimore said.
- Instead: The researchers focused on the cumulative absolutive reduction in elongation (CARE) in diopters (D) or percentages rather than millimeters (mm).
The reason: The slowing of AE in millimeters tends to be interpreted as a constant across both races and ages, he said. And this isn’t entirely accurate.
- In fact: “If you express AE as a percentage, the treatment efficacy would be above 100% in older patients—but only about 30% in younger patients,” according to Dr. Bullimore. “So that slowing of AE (in millimeters) would be the same between both groups.”
What other research has been done on this?
A 2021 study published in Progress in Retinal and Eye Research noted that a relatively large variance of refractive error measurement can “lead to children who are true fast (myopia) progressors not being treated.”
Further, investigators noted that while practitioners “should be aware of the pitfalls of basing clinical decisions on refractive error measurements,” using “axial length to monitor progression does not mean refractive error is of no value when treating myopia.”
Their solution: Establish “predictive markers” to identify patients who are more likely to progress at a faster rate as well as treatments that will most benefit them (ie: CARE).
“CARE is not time independent, an important limitation, and so should be expressed with reference to the time scale,” they wrote.
Interesting … go on.
Also of interest is the efficacy of myopia treatment, which is “larger than that achieved into the second or third year, or thereafter,” Dr. Bullimore said.
With that in mind, he noted that the 3-year treatment efficacy is about twice that of the first-year efficacy.
“We’ve gone so far as to look at 3-year clinical trials, which have demonstrated that you can accurately predict the 3-year treatment efficacy by doubling that first year of efficacy,” he added.
Break this down for me (numerically-speaking, that is).
Based on the researchers’ inferences, the following treatment efficacies would be true:
- Mean 3-year efficacy → 2 x 1-year efficacy
- Mean 6-year efficacy → 3 x 1-year efficacy
- Mean 12-year efficacy → 4 x 1-year efficacy
As such: Over 12 years of myopia treatment, an estimated 1.6 D would be the maximum group mean efficacy from current best interventions.
So what’re the key takeaways from this?
Three key points:
- Myopia in a pediatric patient will progress faster in the first year than it will in subsequent years—and the rate of progression will slow with it
- Treatment efficacy (ie: the slowing of myopia progression) is greater in the first year than in subsequent years
- Clinicians should avoid “over-promising” treatment results to patients
In regards to that last point, Dr. Bullimore noted that, “Yes, a clinician can slow myopia down—and even stop it in older children—but in younger children, their progression rates will be so high that stopping disease progression completely isn’t likely.”
And how can clinicians use these findings in practice?
The researchers have generated a normal growth curve that shows what an average (normal) progression of untreated myopia should look like in a myopic child to assist clinicians in determining whether a treatment is effective in their own patients.
“Of course, not all children are ‘average,’” Dr. Bullimore noted. “So if a clinician is using effective treatments for their patients, nearly all of the treated children should be below that average untreated line; that’s where they should be aiming.”
Anything else?
Most importantly: A clinician should have a better understanding of what to expect from the efficacy of treatment in their patients—and, once again, avoid over-promising results to their patients.