Development of a Novel Multi-Stimulus Ocular Surface Aesthesiometer System

Aims/Purpose: To report the development of a novel, air‐based, aesthesiometer capable of producing and applying multiple stimuli of differing intensity, separated by time and/or ocular surface location. Methods: Individual micro‐blowers (Murata Manufacturing Co., Japan) were combined with an exit airflow nozzle into an integrated stimulus unit (ISU) that produced a controlled exit airflow through the nozzle exit. Stimulus intensity, duration, and repetition, as a feature of airflow, was managed for each ISU using a designed software. The software also controlled stimulus sequencing for multiple ISU in series. Stimulus airflow consistency and characteristics were assessed using two nozzle diameters (0.5 and 1.6 mm) for: (i) airflow pattern/trajectory; (ii) airflow surface dispersion; (iii) force of airflow; (iv) thermal effects; (v) time delay and spatial separation. Results: Stimulus characteristics: (i) airflow is coherent at proposed test distance (1 cm) and spread rate is constant irrespective of stimulus strength, airflow diameter at 1 cm: 1.8–2.1 mm; (ii) airflow disperses over surface and dispersion increases with increasing airflow rate; (iii) consistent, small force (10 −4 N) is produced and varies with airflow rate; (iv) size of thermal effects depends on airflow rate; (v) single stimuli, repeat single stimuli with variable time‐delay, simultaneous multiple stimuli or with inter‐stimulus time delay can be produced. Conclusions: The novel ISU can produce repeatable, consistent air pulses (stimuli) under software control. Nozzle diameter has an influence on airflow coherence/dispersion. Single or multiple simultaneous stimuli with/without time delays, of differing intensity and duration, can be delivered to ocular surface. Multiple ISU allows presentation of multiple simultaneous stimuli that may provide an alternative method for assessing ocular surface sensitivity, and facilitate investigation of signal processing involved in ocular surface nerve summation.