Biological Mechanisms of Atropine Control of Myopia

Abstract

Myopia is a global problem that is increasing at an epidemic rate in the world. Although the refractive error can be corrected easily, myopes, particularly those with high myopia, are susceptible to potentially blinding eye diseases later in life. Despite a plethora of myopia research, the molecular/cellular mechanisms underlying the development of myopia are not well understood, preventing the search for the most effective pharmacological control. Consequently, several approaches to slowing down myopia progression in the actively growing eyes of children have been underway. So far, atropine, an anticholinergic blocking agent, has been most effective and is used by clinicians in off-label ways for myopia control. Although the exact mechanisms of its action remain elusive and debatable, atropine encompasses a complex interplay with receptors on different ocular tissues at multiple levels and, hence, can be categorized as a shotgun approach to myopia treatment. This review will provide a brief overview of the biological mechanisms implicated in mediating the effects of atropine in myopia control.

FIG. 1.

Schematic representation of signal cascade mediating myopia development in animal models. The available evidence points to an interaction between the retina and sclera in the development of myopia. However, this is largely from animal model studies where visual cues such as optical defocus imposed by lens wear predominantly drive axial elongation. These visual inputs initiate certain molecular events in retina. The growth-regulatory signals are then relayed to the sclera through RPE and choroid to facilitate programs of gene expression, cell proliferation, and scleral remodeling, which subsequently lead to axial length elongation causing myopia. We have little idea as to the situation in humans, where genetic and environmental factors may also play a role in myopia induction and development. Moreover, we do not know the nature of intertissue communication that may be quite complex in humans and even change in different stages of myopia development. Atropine targets biological receptors in both the retina and sclera, to curtail myopia progression. RPE, retinal pigment epithelium.