Optical magnification in surgery and dentistry enhances vision, ensures accuracy of delicate procedures and improves the ergonomics of working conditions. When selecting magnification loupes, surgeon needs to consider several optical features: working distance, depth of field, field of view, convergence angle, exit pupil, entrance pupil. To understand these aspects, it is essential to know basic optical principles and functioning of optical systems. Long-term use of poorly fitted and wrongly adjusted loupes can result in eyestrain, fatigue, neck, back and shoulder pain and even vision impairment. The authors describe basic optical principles and main features of surgical telescopes, various types of loupes, features of their settings and adjustments. These data will be valuable in choosing the optimal optics and enjoying all benefits of optical magnification.