A novel method to stimulate mechanoreceptors and quantify their threshold values. (10th January 2018)

• Record Type: Journal Article
• Authors: Ehrmann, Klaus; Saha, Mou; Falk, Darrin
• Is Part Of: Biomedical physics & engineering express. Volume 4:Number 2(2018)
• Publication Date: 2018-01-10
• Subjects: esthesiometer -- corneal sensitivity -- mechanoreceptors -- liquid jet; Medical physics -- Periodicals; Biophysics -- Periodicals; Biomedical engineering -- Periodicals; Medical sciences -- Periodicals; 610.153
• DOI: 10.1088/2057-1976/aa9b8d
• Languages: English
• ISSNs: 2057-1976

Abstract

Abstract: The increase in the incidence of ocular discomfort has primarily been attributed to: contact lens wear, refractive surgery, meibomian gland dysfunction, and the aging population. Efforts to diagnose, treat and understand the underlying causes have been impeded by a lack of suitable methods to quantify ocular surface sensitivity. Traditional instruments are either inaccurate, difficult to use or not generally available. A new method is presented that utilizes a liquid jet to generate a precisely controlled stimulus to the ocular surface. The stimuli are adjustable in strength to determine sensitivity thresholds for either mechanical, thermal or chemical stimulation. Technical details are described and calibration methods and results are presented for three modes of operation. At the heart of the instrument is a microprocessor controlled microvalve which can operate at a frequency of up to 4 kHz to precisely control flow of the ejected liquid. The stimulus strength can be varied either by the ejected volume or the velocity. Repeatability for the ejected volume was established over a range of different control parameter settings: temperature, pressure, working distance, operating mode and volume. For 10 repeats, the maximum standard deviation was less than 3% of the mean of ejected volume for any particular setting. The maximum error for the lateral targeting of the liquid jet for the 30 mm distance between nozzle and target surface was less than ±0.5 mm. A simplified mathematical model is presented to physically quantify the stimulus strength. Based on the liquid jet concept, a new instrument was developed and technically validated that can apply a precisely controlled stimulus to an ocular surface to determine mechanical, and potentially thermal and chemical sensitivity threshold levels. The strength and the positioning of the applied stimulus can be precisely controlled. Temporal and spatial aspects of corneal sensation can also be investigated with this new instrument.