1. Medical Faculty, Department of Ophthalmology, University of Nis, Nis, Serbia
2. Community Health center Nis, Nis, Serbia
3. Clinic for Anesthesiology and Intensive Care, Clinical Center Nis, Nis, Serbia
4. Faculty of Medicine, Department of Chemistry, University of Nis, Bulevar Dr Zorana Đinđića 81, 18000 Nis, Serbia