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R.F. See, B.C. Dodge, R.F. Overaker, R. Nappi, M. Stopa, C.A. Toth; Intensity Controllable Hand–Held Surgical Light . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5516.
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Purpose: To develop a novel device (intensity controllable hand–held surgical light) for the control of the illumination source intensity by the surgeon during vitrectomy surgery; and to evaluate the impact of use of this device on the amount of radiant energy delivered to the macula during specific vitrectomy steps. Methods: An intensity controllable hand–held surgical light (light control) was developed working from surgeon goals (such as continuous control without absence of illumination) towards an end product followed by ergonomic testing. Porcine cadaver eyes were used for the simulated vitrectomy procedures with assigned macular tasks. In Test 1 the surgeon did not have direct control of the illumination intensity. After training on the new handpiece, in Test 2 the surgeon used light control. The light intensity was recorded throughout each task as was the overall time to perform the surgical task. The radiant energy delivered within the eye during the task was calculated. Results: Engineering design based on surgeon parameters and ergonomic testing produced a handpiece with an encircling membrane switch located adjacent to the site of normal instrument grasp. The membrane switch assembly provided the surgeon with direct control of the illumination intensity at the light source throughout surgical maneuvers. When the membrane switch was activated it increased or decreased the opening in a shutter assembly to allow light to pass from the source to the fiber optic. There was no position in which the shutter was completely closed, thus ensuring that the light would not be completely blocked by activation of the switch. In simulated vitrectomy tasks there was a difference in the patterns of light use by surgeons in Test 2 when compared to Test 1; however these patterns varied among the test surgeons. Total radiant energy delivered to the eye also varied between Test 1 and 2, primarily due to the adjustment of illumination during tasks using the light control system. Conclusions: Retinal light toxicity occurs through mechanisms involving thermal or photochemical effects, and the mechanism activated depends on the intensity of light, wavelength and duration of exposure. New illumination systems with potentially greater irradiance than currently utilized in surgery are increasing in use in vitreoretinal surgery. Placing control of the light source illumination intensity in the surgeon’s hands is likely to increase the safety of macular surgery by allowing the surgeon to dim the light when not required without adversely affecting operative time.
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