A compact laparoscopic probe for optical stimulation of the prostate nerves

The cavernous nerves (CN) course along the prostate surface and are responsible for sexual function. Optical nerve stimulation (ONS) has recently been tested as a potential alternative to electrical nerve stimulation for identifying and preserving these delicate nerves during prostate cancer surgery. However, the optimal range of laser parameters for safe and consistent laser nerve stimulation is relatively narrow; low-level irradiation may not stimulate the nerve, while high-level irradiation may result in thermal damage to the nerve and loss of erectile function. The objective of this study is to design, build, and provide preliminary data on testing of a laparoscopic probe capable of delivering a collimated, flat-top spatial beam profile to the nerve surface for uniform, safe, and reproducible irradiation of the nerve. Chemical etching of the distal fiber optic tip in combination with an aspheric lens resulted in a 3.4-mm-OD laparoscopic probe capable of delivering a collimated 1-mm-diameter, flat-top laser beam over a working distance of about 20 mm. Successful ONS using this probe was observed in a rat prostate model, in vivo. Upon further testing, this probe may be useful for identifying and preserving the CN during laparoscopic nerve-sparing prostate cancer surgery.