Instruments: Crossing the threshold

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Professor David Henson has been a key researcher and developer of field assessment instrumentation for several decades now. Previous Henson units are commonplace in most high-street practices. Here they are widely used for suprathreshold screening of patients, often as part of a pre-screening process. Their speedy performance and ease of use makes them ideal as a screening tool, capable of being used reliably by trained auxiliary staff, and producing results that are easy to interpret and indicate whether further investigation is needed. The default suprathreshold strategy of running stimuli at 5dB above a measured threshold value offered enough specificity for it to be easy to pass if 'normal' and enough sensitivity to pick up most significant central loss.