Contact Detection of Forceps for a Vitreoretinal Surgical Simulator Using Infrared Reflection Images of Forceps

To train for vitreoretinal surgeries, such as peeling of the inner limiting membrane, a surgical simulator with an elaborate retinal model and method of contact detection is necessary. Quantitative evaluation of forceps contacts to the retinal model is required because excessive forceps contact can cause loss of eyesight. This paper presents a detection method using image analysis to detect forceps contact with the retinal model. An evaluation system for contact detection of forceps was constructed, which includes an optical system incorporating an 850 nm LED, a CCD camera, and an infrared pass filter placed under a retinal model. This system observes the reflected light of infrared light at the forceps tips and evaluates the variation of the forceps shape. The luminance value of the forceps tips edge was set as a common threshold used for each frame and the number of pixels with luminance higher than the threshold was counted before and after forceps contact. As a result of image analysis, we confirmed that the number of counted pixels increased immediately after forceps contact and by evaluating the change in the number of counted pixels, we succeeded in detecting forceps contact at a load of less than 0.1 mN within a radius of $2 \mu \mathrm{~m}$.