The purpose of this study is to objectively and quantitatively estimate the visual fatigue caused by VDT work through analysis of pupillary light response with minimum constraint of subjects. Three experiments were performed as follows. First, the effect of retinal dark adaptation on the pupillary dynamics was analyzed. Secondly, pupillary light response and CFF were measured before and after the VDT task. Thirdly, the relation between visual fatigue and visual organs was investigated. Results were as follows:(i)Such staticcharacteristics of the pupil as an initial diameter change with the retinal adaptation, while, the dynamic characteristics do not.(ii)The adverse effect of VDT work reduces the constriction and dilatation velocities of the pupil.(iii)The changes in the pupillary dynamics are mainly brought about by an elevated state of the parasympathetic nervous system caused by VDT work.

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As a plaque control method, the removal of calculus deposited on the teeth surface is indispensable in the prevention and treatment of periodontal disease. The hand scalar, which is used for removing calculus, must be sharpened just after used it in order to keep it original sharpness. But the qualitative checking method is not established yet. The authors have designed and made an apparatus as an experiment for the evaluation of a model scalar' s sharpeness. The model scalar is straight and large as compared with a real hand scalar. This report deals with the apparatus and it's chracteristics.The ranges of rake angles of the scalers covers from-20deg to 0 deg, and speeds of the bed on which the model teeth(test piece)is fixed from0.5mm/ sec to3.0mm/ sec. Vertical pushing force of the scalar to the test piece and cutting resistance are measured by the use of strain gages. Metals such as steel and aluminum, glass are used as the material for the model teeth.Plastics cement which were dripped on the surface of model teeth are used as the material of calculus. After the cement became solid and set up the parameters such as speed of the bed and pushing force to the scaler, it is ready to scrub away the cement. In the case of the dripped cement were removed and impulsive force data were observed, then it may conclude that the scaler is sharp.

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