Ocular surface temperature in patients with evaporative and aqueous-deficient dry eyes: a thermographic approach

Objective: In recent decades infrared thermography (IRT) has facilitated accurate quantitative measurements of the ocular surface temperature (OST), applying a non-invasive procedure. The objective of this work was to develop a procedure based on IRT, which allows characterizing of the cooling of the ocular surface of patients suffering from dry eye syndrome, and distinguishing among patients suffering from aqueous deficient dry eye (ADDE) and evaporative dry eyes (EDE). Approach: All patients examined (34 females and 4 males, 23-84 years) were divided into two groups according to their Schirmer I result (<= 7 mm for ADDE and > 7 mm for EDE), and the OST was recorded for 7 s at 30 Hz. For each acquisition, the temperatures of the central cornea (CC) as well as those of both temporal and nasal canthi were investigated. Main results: Findings showed that the maximum temperature variation (up to 0.75 +/- 0.29 degrees C) was at the CC for both groups. Furthermore, patients suffering from EDE tended to have a higher initial OST than those with ADDE, explained by the greater quantity of the tear film, evenly distributed over the entire ocular surface, keeping the OST higher initially. Results also showed that EDE patients had an average cooling rate higher than those suffering from ADDE, confirming the excessive evaporation of the tear film. Significance: Ocular thermography paves the way to become an effective tool for differentiating between the two different etiologies of dry eye syndrome.