Quantitative assessment of degradation of the optical quality of rigid endoscopes in clinical practice

To improve efficiency and diagnostics, an optical testbench was developed for routine assessment of the optical quality of endoscopes during their lifespan. An endoscope is positioned on an optical bench looking at a small LCD screen showing computer generated test targets. Images through the endoscope are captured by a high-resolution USB-2 camera, analyzed with dedicated software and stored in a database. Additionally, the transmission of the illumination fibers of the endoscope is determined using a calibrated LED light source and a photo cell. The database enables the tracking of the degradation of each endoscope over time and comparison with other endoscopes of the same type. Using the data collected and the optical quality of new endoscopes as reference, criteria are developed to reject endoscopes at some point in their lifespan. Experience with the optical testbench over the last two years shows that: 1) Optical quality can be measured reproducible over time, 2) degradation in optical quality is often gradually, but may also occur suddenly, and 3) there is a large variation (>20%) in optical quality of new or repaired endoscopes. Routine quantitative assessment of the optical quality of endoscopes will contribute to the efficiency and the quality of surgery.