The development of an objective test method to evaluate the (optical) quality of rigid endoscopes at the CSSD

Abstract

The quality of rigid endoscopes deteriorates during clinical use due to the sterilization process, mechanical forces and wear and tear during regular use. Regulations and standards on ensuring the quality of these instruments are currently non-existent or contain only qualitative measures, resulting in subjective examinations . Defective rigid endoscopes still reach the operating room, resulting in direct and indirect patient risks. An experimental test set-up has been developed to quantify the sharpness, contrast, distortion, light transmission, vignetting and colour correctness of the optical system
of rigid endoscopes. Results are given for 85 measurements performed on 33 endoscopes, including 7 high quality endoscopes and 26 low quality endoscopes. 37 measurements have been performed on a reference rigid endoscope. The results for sharpness, contrast and distortion provide valuable insights but the current design of the test set-up proved not stable enough to draw significant conclusions. The results for light transmission, vignetting and colour correctness produce stable results and display the expected values for damaged lens systems such as loose or broken lenses. Although the current design requires significant optimization, this study has both given an account of the need for an objective method to evaluate the quality of rigid endoscopes as well as provided a promising step towards this new method and greatly encourages further research.