The literature has established that both orthokeratology (ortho-k) and atropine are effective at slowing myopia progression and are increasingly being used clinically, including here in New Zealand. This has led to many clinicians and researchers asking the question, would combining ortho-k and atropine cause a greater reduction in myopia progression?
The exact mechanism of action for these therapies are yet to be confirmed. The working theory, however, is atropine blocks the muscarinic receptors in the retina and sclera to mediate elongation of the globe, whilst ortho-k appears to act on the peripheral retinal defocus. Thus, there could be a potential synergistic effect of combining the two therapies, with some early clinical studies shedding some light on this interesting question.
A retrospective review by Wan et al titled, The Synergistic Effects of Orthokeratology and Atropine in Slowing the Progression of Myopia, was published in the Journal of Clinical Medicine in 2018. The study examined a total of 179 files of patients with myopia who had been prescribed myopia management, either ortho-k monotherapy (n=95) or dual therapy of ortho-k and low dose atropine (n=84). The analysis further divided the groups by spherical refraction into low and high myopia with a cut-off point of over 6D considered high myopia. Those receiving atropine treatment were split again based on the concentration of atropine used, 0.025% or 0.125%. The result of this categorisation is small numbers in each group reducing the statistical quality of these results.
However, regardless of the concentration of atropine used or myopia severity, combination therapy had significantly less axial elongation and less myopic refraction progression than case-matched ortho-k monotherapy patients. This appears to suggest that the combination of ortho-k and low dose atropine may provide improved control of myopia progression than ortho-k alone. This study is, however, retrospective and patients were not randomly assigned to a treatment potentially biasing patient selection. Also, the atropine doses used do not correlate to the 0.01% that is traditionally used in New Zealand, although higher dosages of 0.02% and 0.05% are starting to be used here now too.
A second study from 2018 was a prospective, randomised control trial by Kinoshita et al, which looked at the additive effects of ortho-k and atropine 0.01% in slowing axial elongation in myopic children after one year. The prospective and randomised nature of this study, although small, provides stronger evidence of the impact of the combination therapy of ortho-k and low dose atropine compared to ortho-k alone.
