## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & **DED** & **Control** & \(\mathbf{p}\)**-Value** \\ \hline \multirow{3}{*}{Complete thermal recording (40 s)} & OST (\({}^{\circ}\)C) & 34.8 \(\pm\) 0.7 & 35.0 \(\pm\) 0.6 & 0.308 \({}^{\alpha}\) \\ \cline{2-5}  & OST start (\({}^{\circ}\)C) & 34.9 \(\pm\) 0.7 & 35.0 \(\pm\) 0.6 & 0.363 \({}^{\alpha}\) \\ \cline{2-5}  & OST end (\({}^{\circ}\)C) & 34.8 \(\pm\) 0.7 & 35.0 \(\pm\) 0.6 & 0.411 \({}^{\alpha}\) \\ \cline{2-5}  & TER (W/ m\({}^{-2}\)) & 109.6 \(\pm\) 8.8 & 107.6 \(\pm\) 7.0 & 0.286 \({}^{\alpha}\) \\ \hline \multirow{6}{*}{Last complete interblink interval (100)} & OST-IBI (\({}^{\circ}\)C) & 34.8 \(\pm\) 0.7 & 35.0 \(\pm\) 0.7 & 0.400 \({}^{\alpha}\) \\ \cline{2-5}  & OST-IBI start (\({}^{\circ}\)C) & 34.9 \(\pm\) 0.7 & 34.9 \(\pm\) 0.7 & 0.319 \({}^{\alpha}\) \\ \cline{2-5}  & OST-IBI end (\({}^{\circ}\)C) & 34.8 \(\pm\) 0.7 & 34.8 \(\pm\) 0.7 & 0.722 \({}^{\alpha}\) \\ \cline{2-5}  & TER-IBI (W/ m\({}^{-2}\)) & 109.9 \(\pm\) 8.7 & 108.2 \(\pm\) 6.6 & 0.368 \({}^{\alpha}\) \\ \cline{2-5}  & OST-IBI start min (\({}^{\circ}\)C) & 33.5 \(\pm\) 1.5 & 33.6 \(\pm\) 1.4 & 0.716\({}^{\beta}\) \\ \cline{2-5}  & OST-IBI start max (\({}^{\circ}\)C) & 36.0 \(\pm\) 0.6 & 36.1 \(\pm\) 0.6 & 0.314 \({}^{\alpha}\) \\ \cline{2-5}  & OST-IBI end min (\({}^{\circ}\)C) & 33.6 \(\pm\) 1.2 & 33.5 \(\pm\) 1.6 & 0.437 \({}^{\alpha}\) \\ \cline{2-5}  & OST-IBI end max (\({}^{\circ}\)C) & 35.9 \(\pm\) 0.7 & 36.1 \(\pm\) 0.6 & 0.328 \({}^{\beta}\) \\ \hline \hline \end{tabular}  
* OST: ocular surface temperature; OST start: OST at the start; OST end: OST at the end; TER: tear evaporation rate; OST-IBI: ocular surface temperature in the interblink interval; OST-IBI start: ocular surface temperature in the interblink interval at the end; TER-IBI: tear evaporation rate in the interblink interval (units: W/ m\({}^{-2}\), power loss per area); OST-IBI start min: the minimum value of OST at the beginning of the IBI; OST-IBI star max: the maximum value of OST at the beginning of the IBI; OST-IBI end min: the minimum value of OST at the end of the IBI; OST-IBI end max: the maximum value of OST at the end of the IBI. \({}^{\alpha}\) T-test (parametric); \({}^{\beta}\) Mann–Whitney test (non-parametric).  
\end{table} 
Table 1: Thermographic data for the complete 40 s of sequence and for the last complete interblink interval (IBI). Conversely, a study conducted by [PERSON] et al. showed an increased mean OST in DED subjects (32.38 \(\pm\) 0.69 \({}^{\circ}\)C) in comparison to controls (31.94 \(\pm\) 0.54 \({}^{\circ}\)C) [21]. The authors attributed the higher OST in DED patients to inflammation or increased hyperemia [21; 39]. Additionally, other research studies reported no significant difference in the mean OST immediately after eye-opening between DED and control subjects [40; 41]. Concerning tear evaporation, a wide range of results has been reported [42]. The outcomes of the current study showed no differences in TER between groups. [PERSON] et al. found higher tear film evaporation rate, lower tear film stability and lower OST in DED eyes compared to healthy eyes [22]. [PERSON] et al. found significantly higher TER in DED patients compared to normal eyes, suggesting that this high rate is caused by a decreased tear production, exacerbating DED [43]. However, it should be noted that the studies previously discussed performed the thermal analysis under controlled blinking conditions, in opposition to the current work, which might explain the differences with our results. As previously stated by [PERSON] and [PERSON], the blink action brings the tear film and the ocular surface into close contact with the vascularized palpebral conjunctiva, maintaining the temperature constant [24]. While the eye is opened, the ocular surface temperature decreases. Hence, maintaining the eyes open longer than the normal blinking could increase the overall TER and decrease the average temperature, exacerbating the differences between DED and healthy subjects.