1. Medical Faculty, University of Novi Sad, 21000 Novi Sad, Serbia
2. Eye Clinic, Clinical Center of Vojvodina, 21000 Novi Sad, Serbia
3. Medical Faculty, University of Niš, 18000 Niš, Serbia
4. Eye Clinic, Clinical Centre Niš, 18000 Niš, Serbia
5. Medical Faculty, University of Belgrade, 11000 Belgrade, Serbia
6. Eye Clinic, Clinical Center of Serbia, 11000 Belgrade, Serbia