This blog post is a more detailed discussion of the main studies that are summarized in the post entitled An eye drop to slow nearsightedness.
ATOM 1
The ATOM study published results in 2006. The ATOM researchers studied the effect of atropine 1% on myopic Asian children. In the two years of treatment, the untreated group saw almost 1 diopter MORE progression than the group treated with atropine 1%, and 0.4mm MORE of an increase in axial length. So one drop nightly of atropine 1% resulted in a nearly 80% reduction in refractive error progression, and essentially no increase in axial length (1). The downside of 1% atropine: the adverse effects of blurry near vision, pupil dilation, and light sensitivity are significant. This study actually only treated one eye per child, so that the children were not too debilitated by those side effects. When the participants were taken off the medication at the two year mark, there was “rebound” effect. Rebound means that the atropine-treated group progressed more quickly over the next year than the untreated group did. But the overall effect over three years (treatment for two years, then discontinued for one) still showed significantly less myopia progression in the treated group (2).
It is worth noting that even at this high concentration, there was still progression of myopia amongst the study participants. So our goal with atropine therapy, as with all myopia management strategies, is not STOPPING myopia, but SLOWING its progression.
ATOM 2
The ATOM 2 study assessed lower concentrations of atropine. Unlike the ATOM 1 study, both of the children’s eyes were treated. The researchers tested three concentrations of atropine (0.5%, 0.1% and 0.01%) and found all three to slow the progression of refractive error and axial length. There was a dose-dependent response, meaning that the highest dose, atropine 0.5%, was most effective in slowing myopia, but also had the most adverse effects. Like the ATOM study, ATOM 2 also discontinued treatment after two years, which showed a dose-dependent rebound effect. That means that the higher the concentration, the more rapid the myopia progression once treatment is stopped. The participants that experienced a large rebound (which was over half of the participants) were then restarted on 0.01% for another two years. Over the five total years, atropine 0.01% was of comparable efficacy as the higher two concentrations, but with the least side effects (3). Atropine 0.01% showed a 59% slowing in refractive error, but the axial length change was significantly less impressive. This lack of correlation may suggest that atropine 0.01% isn’t as effective as the study makes it seem. It is also worth noting that this study didn’t have a control group.
So the results of this study led many eye care providers to prescribe 0.01% atropine for myopia management, until…
LAMP
The LAMP study’s design was a bit better than ATOM 2; it was a randomized, double-masked, placebo-controlled study. Atropine 0.05%, 0.025% and 0.01% were used in this study, testing these concentrations against one another and against the placebo/control (which was 0.9% sodium chloride). Like the ATOM 2 study, the LAMP study showed a dose-dependent response. The LAMP study found that all three concentrations were well tolerated without an adverse effect on vision-related quality of life. Atropine 0.05% was found to be the most effective in controlling axial length and refractive error progression, slowing 1-year progression by 0.54 D and axial elongation 0.21 mm (4). The same trend was seen at year two; the efficacy of atropine 0.05% was double that of atropine 0.01% (5).
The phase 2 report of the LAMP study concluded that after 2 years, the 0.05% atropine group saw double the efficacy that the 0.01% atropine group saw, making 0.05% the optimal concentration for slowing myopia progression (6). The phase 3 report found the same after 3 years (7).
Fu et al
A recent study by Fu et al. compared the effects of atropine 0.01% and 0.02%. They found that the atropine 0.02% group had a slightly greater reduction in myopia progression than the atropine 0.01% group after one year of treatment. The two groups showed similarly mild adverse effects, as measured by pupil diameter and accommodative amplitude (8).
To read more on this topic, head over to the previous post.