Effect of Low Concentration Atropine Eye Drops on Choroidal Thickness, Central Corneal Thickness, Anterior Scleral Thickness and Axial Length in Myopic Children

Myopia is the most common refractive error, and its prevalence rate is increasing worldwide, as per WHO, it is projected to increase from 22% in 2000 to 52% by 2050. It is more prevalent in developed, industrial areas and affects individuals of all ages (Singh et al., 2022). Myopia, especially the degenerative type, is associated with sight-threatening complications, including presenile cataract, glaucoma, retinal detachment, choroidal neovascularization, myopic macular degeneration, scleral and choroidal thinning (Sanchez-Cano et al., 2014 and Gupta et al., 2015) which makes myopia a major public health concern and finding an effective treatment to prevent myopia progression is critical (Wakazono et al., 2016).

Atropine is a nonselective muscarinic antagonist used for myopia control in previous studies. However, its actual mechanism of action is not well known (Yam et al., 2019).

But different mechanisms were described, first mechanism, that atropine may induce release of dopamine causing thickening of choroid (Nickla et al., 2010) Second mechanism,blockage of choroidal smooth muscle contraction through its anti-muscarinic action. Third one, increasing capillary permeability. Fourth, potentiating the synthesis and release of intraocular nitric oxide (Yam et al.,2022) also it stimulates retinal expression of the transcription factor ZENK which was considered an eye growth-inhibiting signal (Torii et al., 2017). All these mechanisms cause thickening of the choroid and increased choroidal blood flow which has been found to play a role in the regulation of eye growth and refractive error development through inhibition of the penetration of various retinal-derived growth factors that act as mechanical barriers and slow scleral growth (Nickla et al., 2015 & Guggenheim et al., 2011). Also, choroid can secrete growth factors that prevent scleral hypoxia (Wu et al., 2018).

According to the Low-concentration Atropine for Myopia Progression (LAMP) study, different atropine eye drops concentrations 0.05%, 0.025%, and 0.01% controlled myopia progression but the most effective concentration on spherical equivalent and axial length progression was 0.05% (Yam et al., 2019).

Zhang et al. reported in 2016 that administration of 1% atropine gel increased the choroidal thickness in young Chinese children with inhibition of eye growth.