Many studies have shown that both genetic and environmental factors contribute to the pathogenesis and progression of myopia. The latter most commonly influence major changes in the prevalence and severity of myopia and, for this reason, current myopia drugs are primarily aimed at inhibiting the effects of environmental factors. In contrast, genetic factors can influence the pathophysiology of myopia at various levels and potentially affect the pathways that mediate the effects of environmental factors.
This optical condition is caused by a refractive error, often resulting from a mismatch between the refractive power and the axial length of the eye, whereby the image of distant objects is formed in the eye in front of the retina, making their vision indistinct and blurred, while the vision of the same objects at a short distance remains clear and distinct. A high degree of myopia can increase the risk of potentially dangerous eye diseases such as glaucoma, cataracts and retinal detachment. Therefore, it is crucial to prevent the onset and progression of myopia early, especially among young children, to reduce the risk of high myopia in adulthood.
To date, optical correction with traditional lenses or contact lenses is useful to enable correct vision in myopic individuals, but it is not sufficient to stop the progression of myopia. But will it be possible to treat myopia with medication in the future?
Drugs for myopia
Although myopia results from interactions between genes and environment, pharmacotherapy remains a potential treatment modality. Among the most studied pharmacological therapies are atropine-based topical eye drops, which, however, are still awaiting approval by pharmacovigilance bodies.
In an analysis comparing as many as 30 clinical studies, it was reported that pharmacological interventions, including those based on atropine and pirenzepine, are effective in slowing down refractive change or axial lengthening. However, the optimal dose of atropine still remains unclear and will need to be further investigated with further studies.
Researchers are also working to identify other candidate drugs such as α2-adrenergic receptor agonists and metalloprotease inhibitors. The role of dopamine signalling in the interaction between genetic and environmental factors in the pathogenesis of myopia could be another interesting target for the pharmacological treatment of myopia. Furthermore, further studies will be needed to understand the additive effect of a combination of pharmacological agents with optical and environmental interventions.
Gene therapy for myopia
The identification of genes associated with myopia susceptibility could clarify the molecular basis of this condition and the possibility of using gene therapy. Genome-wide association studies (GWAS) have identified that genes proximal to loci associated with myopia or refractive error are involved in several pathways, including remodelling of the extracellular matrix of the sclera, ocular and central nervous system development, neurotransmitter function, neuronal development, and retinoic acid metabolism.
In general, for drug therapy or gene therapy to control myopia, it will be important to determine whether the target of treatment is the sclera or the retina. From a pharmacological point of view, scleral tissue can be reached more easily through topical eye drops than retinal tissue. In addition, prophylactic use among children at high risk of high myopia should also be considered when establishing an optimal and safe therapeutic dose of atropine.
In conclusion, an optimal pharmacological treatment modality has yet to be developed. Currently, ortho-K (i.e. night-time contact lenses), soft multifocal contact lenses and atropine are among the recommended therapies. For each of them, ophthalmologists consider the efficacy, associated risks and benefits, along with the effect of environmental factors. In fact, drug treatment, optical treatment or combination therapy should be performed taking into account environmental conditions (such as increasing outdoor activities or reducing the duration of myopia-promoting activities) to effectively reduce the progression of myopia or inhibit its pathogenesis in the future.
Bibliography:
Dr. Carmelo Chines
Direttore responsabile
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