Myatro drop contains 0.01 %atropine. This low concentrations atropine is proved to prevent the myopic number in children but not cylinderical power. High myopia means power more than -5D may have many complications. So early halt on progression of myopia(glass power)  is beneficial. It should be used once in night for atleast 2years. With that outdoor activities and decreasing the duration of near work like digital devices have been reported very helpful. And monthly follow up is needed for thorough slit lamp examination and glass power and compliance and any side effects. use of atropine eye drops may lead to photophobia, blurriness of near vision, and local allergic response but they are very rare with this low concentration of atropine. ask your treating ophthamologist for further details