1. Department of Pediatric Hematology and Oncology University Hospital Essen Essen Germany
2. Department of Ophthalmology University Hospital Essen Essen Germany
3. Department of Pediatric Hematology and Oncology Charité‐Universitätsmedizin Berlin Berlin Germany
4. Institute of Biostatistics and Clinical Research University of Münster Münster Germany
5. Department of Ophthalmology Charité Berlin Berlin Germany
6. Department of Diagnostic and Interventional Radiology and Neuroradiology University Hospital Essen, University of Duisburg‐Essen Essen Germany
7. West German Proton Centre University Duisburg‐Essen, University Hospital Essen Essen Germany
8. Institute of Human Genetics University Hospital Essen, University Duisburg Essen Essen Germany
9. Pediatric Oncology and Hematology, Children's Hospital Eberhard Karls Universität Tübingen Germany
10. Department of Ophthalmology Univ.‐Klinikum Graz Graz Austria
11. Department of Ophthalmology Eberhard Karls Universität Tübingen Germany
12. Department of Pediatric Oncology Univ.‐Klinikum Graz Graz Austria