Long term stability of sensation thresholds from 10 millisecond pulses of 2.01 micrometer laser light

Abstract

Current methods for diagnosing and evaluating efficacy for treatment of diabetic neuropathy either give only subjective data or are invasive. However, the use of laser induced sensations to evaluate threshold sensations gives precisely quantifiable and reproducible stimulus and is 100% non-invasive. In this study we evaluated whether or not laser sensation thresholds were stable in 12 human subjects over a four month period of time. Subjects' hands and feet were exposed over eight different exposure sessions to 10 ms pulses of laser light produced by a 50 W Tm: YAG laser system. Sensation threshold values (in mJ/mm2) were determined for each session and compared by regression analysis. The results showed an upward trend in sensation thresholds over time in the majority of the subject's hands and feet, indicating that laser sensation thresholds are not stable over time. Subject desensitization to the sensation over time combined with too short a time between exposures, or variations in baseline skin temperature of the exposure site due to changes in weather are discussed as possible causes of the upward trend. Finally, suggestions are made for future studies to include a study over a longer period of time with more time between exposure sessions and more subjects as well as a study where the exposure sites are heated/cooled to a standardized baseline temperature prior to each exposure session.