We know that low dose atropine has been used to control myopia progression for a number of years now. It is still not approved by the US or Chinese FDA partially because long-term safety data are lacking. Previous studies demonstrated 2 years of using to be safe and effective. But myopia control is a long-term thing, maybe up to 10 years if a child starts to develop myopia from an early age (6- 8 years of age).
Well now there is a study in Taiwan following children using low dose atropine for 10 years. This is a cohort study, no controls, and with only 23 subjects. Every child (that had myopia) was on low dose atropine for the entire 10 years and monitored every 2-4 months to check their refraction and axial length. It is certainly not a controlled or randomised study, and with a low sample size. However, I think it gives us a lot of information in a clinical setting on what to expect once a child is on low dose atropine for myopia control long term.
They also adopted a commonly used clinical approach, stepwise increase in treatment dosage if the treatment effect is not enough. For example, every myopic child started with 0.05% atropine. If a child did well on this, they continued this dosage throughout the 10 year period. If however their myopia continued to progress more than 0.50 D every 6 months, then they were switched to higher concentrations of 0.1%, 0.25%, and until 0.5%. A high concentration of 1% was not used.
In my clinic (and perhaps many others), I usually start with even lower concentration, 0.01%, which has been clinically proven to be effective in myopia control and with the least side effects including pupil dilation, light sensitivity and blurry near vision. I would go up to 0.02% and 0.05% if myopia control is not achieved, and I seldom go higher than 0.05% because at this point the side effect is noticeable and may interfere with normal study and life of a child. Eye doctors in Taiwan are more aggressive in myopia control in terms of using atropine and I thank them for the study. I always wonder whether I should ramp it up, and if higher concentrations are effective, then maybe it’s worth the side effects (and potentially risks of using this for 10 years).
This study answered my question to some degree. First of all, 65% patients were only using 0.05% atropine throughout the study, which means 35% patients did not respond well to the initial low dose. This is a high number. Remember 0.05% is already a higher concentration than the most commonly prescribed 0.01%, and still ⅓ of children do poorly on it. When we encounter children like this (and we will), do we further increase the dosage? In their study they did, and what they discovered was that for those who did not do well in the initial low concentration of atropine, despite the stepwise increase in the atropine concentration, their myopia control was still worse than the kids who responded to the initial low dose atropine. There were vast inter-individual differences, but the mean numbers look like this: the responding kids started with -1.5 D and progressed to -4.7 D after 10 years, whereas the poorly responding kids started with -0.9 D and progressed to -6.6 D. Their study did not have a control, but based on natural history of myopia progression in their population, they predicted about -7.7 D if no myopia control was done at all. So for those that respond to atropine, a reduction of 3 D of myopia over 10 years is quite good, especially it prevents these kids from developing high myopia (more than -6.0 D), which is associated with more retinal related complications. On the other hand, 10 years of high dose atropine in children who were poor responders resulted in only 1 D of myopia reduction, it seemed less worthwhile, considering the burden of using drops daily for 10 years and the side effects associated with dilation. Of course, this is purely based on a mean value, and individuals can be quite different, and for some, maybe 1 D reduction is still something that helps.
But the lesson here is that if a child responds poorly to low dose atropine, merely increasing the concentration may not be the answer. They may be better off with additional or alternative control methods, such as ortho K lenses or multifocal soft contact lenses.
Another outcome is that they did not find significant side effects with 10 year use of low dose atropine drops. The study also claimed that the children were not prescribed PALs. That is interesting, considering that atropine at concentration of 0.1% or above will have significant dilation and cycloplegic effects. Given that they used higher concentrations, it can be assumed that 0.01% atropine can also be used without significant side effects for up to 10 years.
So the take home message is that long term use of low dose atropine (10 years) may be safe and effective, but if a child responds poorly to low dose atropine, then they may benefit more from other methods of control. But keep in mind that this is a limited study with small number of patients. We still wait for larger scale and better controlled study.
The study cited in this article:
Chuang, MN., Fang, PC. & Wu, PC. Stepwise low concentration atropine for myopic control: a 10-year cohort study. Sci Rep 11, 17344 (2021). https://doi.org/10.1038/s41598-021-96698-6