“Lifestyle is by far the biggest factor”

Optometrist and dispensing optician, Jason Higginbotham, hosted a session entitled What is myopia without measurement? at 100% Optical 2023.

Higginbotham began his talk by recapping what practitioners may already know about myopia, including its likely prevalence by 2050, that half of the world’s myopes at this point will still be in Southeast Asia, and how high myopia is now classed by many as being -6 rather than -5.

In one area of Japan, myopia-related eye conditions are the “leading cause of new monocular blindness registrations,” Higginbotham said.

He also emphasised that there is a higher failure rate for high myopes if they have cataract surgery later in life.

Higginbotham went on to explain that he feels myopia management should be renamed ‘axial length management,’ because “high RX does not damage the eye. If you’ve got a high refractive myope, with a steep cornea, and a normal axial wave, they are at no more risk of those other secondary conditions than a hyperope or an emmetrope. It’s the axial length that does the damage.”

“85% of all myopia is axial myopia,” he added: “In general, that is what we are trying to deal with – axial length.”

Determinants and causes

Predictions for myopia prevalence in 2050 might actually be an underestimation, Higginbotham said.

“Lifestyles are changing in such a way that more of us, and more children, are on smartphones more often,” he emphasised.

He went on to outline the definitions of myopia and discuss the determinants and causes of the condition, using papers published by the International Myopia Institute to highlight his points.

There is an “incredibly low prevalence” of myopia in Australia, he noted, which is ironic as it is the part of the world where myopia research has been at the forefront.

He also emphasised the difference between genetic and familial predisposition.

“One of the main determinants that we know of with myopia is the genetic predisposition, which isn’t the same as familial,” he said. “Genetic predisposition is really an ethnicity situation. We know that people from Southeast Asia have a higher genetic predisposition.”

He added: "It’s split into environmental and lifestyle, and then genetics.”

Genetic predisposition might mean that people are more prone to react to the environmental factors that lead to myopia, Higginbotham said: “They may have a much higher rate of change when they do use a smartphone or don’t spend much time outdoors.”

He continued: “One parent will increase the odds by 1.42. But if both parents are myopic, it might be as much as 3.4 times more likely that their child will be myopic. It doesn’t sound like a lot, but it does make a difference.

“Genetic predisposition in terms of ethnicity has a much greater effect on the likelihood of progressing. If you have a genetic predisposition, both parents are myopic, you’re always on a smartphone, you do lots of close work and you don’t spend time outdoors, you can imagine why so many people, particularly in Southeast Asia, are becoming highly myopic – but more and more kids across Europe and North America [are] as well.”

Some parts of South Korea have a prevalence of myopia of 97%, Higginbotham added.

He shared a list of potential determinants from the American Academy of Ophthalmology, which included high IQ, although he added that there is nuance in this: “I don't think the fact you’ve got a high IQ means you're going to be more myopic. If you have a high IQ and you spent your entire childhood outdoors and didn’t do much reading, you’re probably not going to be myopic. It’s more about how you’re more likely to be doing a lot more close work and a lot more study for longer periods.”

He went on to share a slide that highlighted the main theories behind myopia progression, including lag of accommodation, peripheral hyperopic defocus, mechanical tension theory, and sleep deprivation and circadian rhythms.

“Blue light and high contrast have been shown to increase axial length, but also poor sleep patterns, which I think is certainly a problem,” he said. “Blue light affects circadian rhythms. We know that red lights at night are far better in helping children to sleep, and that mimics what happens in the sky.”

While outdoor time is proven to be effective in slowing or halting the onset of myopia, Higginbotham said, “recent studies have shown it is less effective at slowing progression, once myopia has actually begun to develop.”

He went on to discuss contrast theory, backed up by recent studies that suggest prolonged high contrast promotes axial elongation, and that reducing spatial contrast reduces it.

Higginbotham shared the details of a study that started in the 1960s, which showed that in a group of Native Americans in Alaska only two out of the 131 elders had myopia, but that their children and grandchildren had a 50% prevalence of the condition.

He also noted a study of Australia’s Asian population, which showed that those brought up in the countryside had a much lower prevalence than those brought up in cities.

Practical applications

Higginbotham went on to encourage practitioners to engage with the subject in their practices.

“You don’t have to have equipment to do myopia management. You can all do it. If you’re not doing it, I hope you do start, because what you’ve got in practice is enough,” he said.

He emphasised that optometrists do not have to use ortho-K, but “decide what treatments you feel confident with.”

He gave the following advice to any optometrists considering a myopia management offering: “Set your protocols. Assume that all kids are at risk, screen them, and if they’re not great, do something about it. Have a myopia questionnaire: ask them about familial history, genetic history, lifestyle. Ask them when they first started wearing glasses, what their first myopic RX was – all of those things can help you understand.”

There is a myopia predictor on the Brien Holden Vision Institute website that can help practitioners understand where their patients are likely to be in years to come, he said.

He added: “Make sure you feel confident, and that you are trained up. Make sure you know what you’re doing, and if you’re not confident make a note and refer those patients to somebody who is.

“Consider aftercare and follow up, consider a marketing plan, and consider what you are going to charge.”