20. Light sources

Light sources for endoscopic surgery couple focused bundles of white light with the surgical lightguide in the endoscope. Traditional xenon lamps are being replaced by Light Emitting Diodes (LEDs), which are more efficient and require less cooling. A color temperature of about 5,000 K and a Color Rendering Index (CRI) ≥ 90 are advisable. LEDs can be so small that some endoscopes have them in their tip. The biggest challenge in endoscopy is getting enough light inside for good visualization, while avoiding tissue overheating. The term “cold light” is misleading, and the term “heat radiation” does not exist: all light can heat up tissue. The balance of light absorption and reflection determines the induced radiation heat. UV and IR light should only be emitted if they serve the medical procedure (e.g., fluorescence, photo-dynamic diagnosis, photo-dynamic therapy) and are restricted to exposure safety limits. Never neglect light source maintenance, and use original lamps and LEDs!