It has long been recognized that effective teaching of colorectal endoscopy calls for simultaneous observation by the teacher and pupil of the same area and/or lesion. Various instruments have been described from time to time, but none apparently has become popular. Appreciating the need for such a teaching tool, I set out some 15 years ago to design an instrument that would make possible the simultaneous viewing of the examining field by two or more observers. The first effort (fig. 1) consisted of two arms with optical systems mounted on a device with built-in magnifying lenses. This instrument has a screw-on adjustable mechanism, mounted on a Turell sigmoidoscope, that incorporates a dual system of illumination—proximal (the light near the examiner's eye) as well as distal— and suction.1 Although this instrument made possible the simultaneous viewing of one area or lesion by two persons, the range of visibility was too
Turell R. A TEACHING INSTRUMENT FOR PROCTOSIGMOIDOSCOPY. JAMA. 1957;163(1):37–38. doi:10.1001/jama.1957.82970360002008a
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