Repeatability of infrared ocular thermography in assessing healthy and dry eyes

Purpose. To investigate the Inter-image, inter-occasion and inter-examiner repeatability of NEC infrared thermo-tracer TH9260 in assessing healthy and dry eyes. Methods. Ocular surface temperature (OST) was recorded using NEC infrared thermo-tracer TH9260 on 21 healthy and 15 dry eyes. Data from the right eyes were analyzed. Marking of the ocular surface and OST acquisition was performed using a new ‘diamond’ demarcation method. Twelve OST indices were obtained at three different time points: 0 s, 5 s and 10 s. Inter-image, inter-occasion and inter-examiner repeatability of the infrared ocular thermography was evaluated by calculating coefficients of repeatability (COR). Results. Ten out of the twelve tested OST indices had good repeatability with small inter-image variability (%COR: 0.2 to 0.9), inter-occasion variability (%COR: 2.1 to 3.7) and inter-examiner variability (%COR: 1.5 to 3.7) for the three studied time points. Two of the OST indices (temperature standard deviation of the region of interest and radial temperature difference) had poor repeatability with much larger inter-image variability (%COR: 8.9 to 140.7), inter-occasion variability (%COR: 47.5 to 153.5) and inter-examiner variability (%COR: 54.7 to 142.0) for the three studied time points. Conclusions. Most of the metrics adopted in this assessment can be considered to be highly repeatable.