Thermal Variations of Operative Microscopes in Otology

Objectives (1) Measure temperature variations achieved by common otomicroscopes. (2) Raise awareness about possible thermal injury during otologic procedures with the advent of newer, high-powered otomicroscopes. (3) Describe optical technology that aims to reduce the potential for thermal injury. Methods A variety of otomicroscopes, with different light sources (ranging from 100W halogen to 300W xenon), were studied. Temperatures were recorded from human auricular skin with a noncontact infrared thermometer at various microscope light intensities and with use of irrigation. Multiple recordings were done at 5-minute intervals, and a working distance of 225 mm was maintained. Results Maximum skin temperatures were found to plateau relatively quickly, with higher-wattage xenon light sources reaching greater temperatures. One-way analysis of variance revealed significant differences in temperatures with decreased light intensities. High-wattage xenon light sources reached significantly higher temperatures when compared with halogen models. Discussion There is substantial variation in maximal skin temperatures reached by otomicroscopes. Temperatures can be decreased to safe levels by reducing light intensity and with use of irrigation. The maximum temperature obtained in our study was 41.4°C. Second-degree skin burns have been described with prolonged exposures to temperatures >44°C. Implications for Practice Given the described potential for burns, surgeons performing procedures on the ear and temporal bone should take precautions to diminish temperature in the operative field.