A new automated tactility test instrument for evaluating hand sensory function

An automated aesthesiometer for measuring tactile sensitivity when freely probing a tiny gap in an otherwise smooth surface, is described. What distinguishes this test from conventional tactility tests, such as discriminating two-points or detecting a point-pressure, is that it can measure tactile sensitivity using active touch rather than a passive tactile stimulus. Using this apparatus, free finger probing is possible while still maintaining control of important test conditions, including contact force, using a precision constant torque balance beam system. This permits testing tactile sensitivity for common occupational tactility inspection, activities such as sensing surface features like a scratch. A precision gap between 0 mm and 10 mm is controlled using a micropositioner and digital encoder for a measured accuracy of 0.001 mm. Finger contact force is nominally controlled within 1 g for loads between 1 and 100 g. The test Is administered under microcomputer control, making it suitable for use on a table-top in a clinic or in the field. Normative index finger tactile sensitivity thresholds for 15 subjects, using a modified method of limits paradigm, for the dynamic sensory test (mean=0.17 mm) were almost an order of magnitude less than for the static sensory test (mean=1.51 mm)