June 1, 2020
By Dwight Akerman, OD, MBA, FAAO
Myopia is characterized by excessive axial elongation because of an increase in the vitreous chamber depth of the eyes, which causes light from distant objects to focus in front of the retina, leading to the formation of blurred images. In other words, there is a mismatch between the focal length and the axial length of the eye in myopia, with the latter being too long for the refractive power of the lens and cornea. Myopia is a complex multifactorial disorder regulated by interactions between environmental and genetic risk factors and occurs because of failure to achieve or maintain the normal process of emmetropization.
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, there is no established way to prevent the onset of myopia, totally stop the progression or reverse the progression. Most existing strategies to control the epidemic of myopia, thus, aim for effectively managing the disorder by delaying its onset or slowing down myopia progression in the actively growing eyes of children.
Myopia control using pharmaceutical interventions such as atropine has been reported to be most effective in comparison with other strategies. Anticholinergics are a class of drugs that block the action of acetylcholine at the muscarinic receptors (MRs) on structures with parasympathetic innervation and smooth muscles. Pharmacologically, atropine acts as a reversible competitive antagonist with an affinity for all the five subtypes of acetylcholine MRs (MR1–MR5) and thus has been presumed to exert its myopia-protective effect mainly through the MRs. The available evidence points to an interaction between the retina and sclera in the development of myopia. Atropine targets biological receptors in both the retina and sclera, to curtail myopia progression.
Biological Mechanisms of Atropine Control of Myopia
Aradhana Upadhyay, Roger W. Beuerman
Myopia is a global problem that is increasing at an epidemic rate. 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.
Upadhyay, A., & Beuerman, R. W. (2020). Biological Mechanisms of Atropine Control of Myopia. Eye & Contact Lens, 46(3), 129-135.