Subjective Discomfort Symptoms Are Related to Low Corneal Temperature in Patients with Evaporative Dry Eye

Purpose: To measure the corneal temperature in patients with dry eye (DE) and to correlate the values with subjective discomfort symptoms. Methods: Twenty-four patients with DE (scored as DEWS severity grade 2 to 3) and 15 age-matched normal control subjects were enrolled. Subjective symptoms of discomfort were scored with an Ocular Surface Disease Index questionnaire, and a 100-mm horizontal visual analog scale (VAS) technique was used to measure symptom intensity. Schirmer I test, tear film breakup time (TFBUT), and Oxford grade scoring were performed in all subjects. Dynamic infrared noncontact thermal imaging (Tomey TG 1000) was used to measure the central corneal temperature (CCT). After training, subjects were asked to maintain their eyes forcedly open and to signal the discomfort onset time (DOT). The temperature was measured at eye opening (T 0) and every second during 10 seconds of sustained eye opening (T 10). The first discomfort sensation onset time (DOT) was also recorded. Temperature values were correlated with the clinical tests, Ocular Surface Disease Index, VAS, and DOT, and data were statistically evaluated (significance P < 0.05). Results: The corneal temperature immediately after eye opening was significantly lower in patients with DE than in controls, in correlation to the subject age, VAS, and TFBUT. A 3-phase cooling profile in patients with DE and a point of highest decrease (HD) in both groups were identified. DOT occurred earlier in patients with DE than in controls (5.9 vs. 15.9 seconds) and was strongly correlated to the VAS, TFBUT, and CCT-HD. Conclusions: Subjective sensation of discomfort occurred earlier in patients with DE than in controls, in correlation to low corneal temperatures and enhanced tear evaporation. ©