| 摘要 |
In a non-contact type tonometer for blowing compressed gas against an examined eye through a nozzle, when a piston returns to an initial position by a biasing unit for biasing so as to return the piston to the initial position, a piston driving unit is actuated so as to attenuate the piston return speed by applying a force in the upwardly moving direction. Further, the piston is attached a piston rod so as to move in the axial direction of a cylinder, and is provided a gas passage which is closed when the gas is compressed and is opened when the piston returns to the initial position by the movement of the piston rod. Thus, the air compression chamber within the cylinder is caused to conductively connect to the atmospheric open chamber to thereby restrain the interior of the cylinder from becoming negative in pressure. In this way, it is possible to suppress the sucking-in of tears, dust, eyelashes and the like through the nozzle as effectively as possible with a simple structure.
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