Surgical loupes
angulation, HT
Three types of loupes were used in this study: the surgeons’ own traditional nonprismatic loupes (own) with a typical magnification power of 2.5, low-tilt (LT) prismatic loupes (Optergo AB, Mölnlycke, Sweden) with a 15° angulation of the optical axis in the prism and magnification power of 3.0, and high-tilt (HT) prismatic loupes (HOYA Technosurgical, Tokyo, Japan) with an angulation of 48° in the prism and magnification power of 2.5. The LT loupes were custom-made and custom-adjusted for each participant, and the frame provided a fixed forward inclination of 20°. In comparison, the HT loupes were ready-made (not custom-made) with an adjustable inclination angle of the frame up to 30° and were adjusted to fit each participant’s needs before the laboratory trial.