Infrared Ocular Thermography on Dry Eye: Static vs Dynamic Measures

Purpose: To study static and dynamic measures of infrared (IR) ocular thermography in screening dry eye. Methods: NEC TH9260 thermo tracer was used to measure the ocular surface temperature (OST) of 38 dry eye and 42 controls. OST acquisition was undertaken with the OST Analysis VII program. A region of interest (ROI) was demarcated by 5 anatomical points: temporal limbus (LT), nasal limbus (LN), outer canthus (T1), inner canthus (T4) and lowest point of the eye. 4 parameters were studied for static and dynamic measures: geometric center of cornea (GCC), mean ocular surface temperature (MOST), radial temperature difference (RTD) and the standard deviation of temperature across the ROI (SD). For static measures, One-Way ANOVA was performed at 95% CI. For dynamic measures, regression line of mean change over 10 s was plotted followed by unpaired t-test (2-tailed). Net change over 10 s was also studied. Repeatability and reproducibility were studied on 15 randomly selected dry eye and 21 controls. Results: For static measures, dry eye had lower GCC and MOST but higher RTD and SD than controls. Highly significant differences in OST between dry eye and control subjects for GCC, MOST and RTD at 0 s (GCC, p = 0.0004; MOST, p = 0.0002; RTD, p = 0.0024), 5 s (GCC, p = 0.0001; MOST, p = 0.0002; RTD, p = 0.0028) and 10 s (GCC, p = 0.0002; MOST, p = 0.0001; RTD, p = 0.0010) were found. Highly significant differences for SD at 5 s (p = 0.0015) and 10 s (p = 0.0039) but none at 0 s (p = 0.2466) were also found. For dynamic measures, dry eye had greater mean change over 10 s for GCC, MOST and RTD than controls. Mean change over 10 s for SD was similar for both groups. There was no statistically significant difference in mean change over 10 s between dry eye and control subjects for GCC, MOST and SD. However, there were statistically significant differences in mean change between dry eye and control subjects for RTD from 8 s onward. Net change over 10 s of dry eye and controls were statistically different. In this study, IR ocular thermography measurements were found to be highly repeatable and reproducible. Conclusion: Both static and dynamic measures have potential for screening dry eye. Static measures were however, more effective than dynamic measures.