One current evidence-based method to control myopia progression in children is the use of atropine, a non-selective muscarinic antagonist. The SAM-IIT study performed at the University Eye Hospital Tuebingen and the STZ eyetrial investigates the safety and tolerability and a possible myopia control effect of low-dose atropine (0.01 %) in children and adolescents between 6 to 17 years with progressing myopia over a 13-month period. As part of this project, we assess whether the treatment with atropine leads to concomitant anatomical changes of the ciliary muscle.