Abstract
Purpose :
To determine the decay rate of corneal surface temperature along the interblink period in dry eye patients.
Methods :
Corneal surface temperature (CST) values were measured from images taken with an infrared video camera (InfRec R300SR, Nippon Avionics), using dedicated software. In healthy subjects and in dry eye patients, temperature at the center of the cornea was measured immediately after a voluntary blink. Also, successive temperature values along the interblink interval were measured and used to calculate the slope of temperature change. All subjects were explored with the McMonnies questionnaire adapted for Spanish speaking people, Schirmer test, BUT and corneal fluorescein staining. Subjective sensations of discomfort were also scored using a visual analog scale.
Results :
Twenty four patients (21 female/3 male; 53 ±11 years) already diagnosed of Sjögren’s syndrome (SS) and eighteen control subjects (13 female/5 male; 47±8 years) participated voluntarily in the study. All clinical variables were significantly different in SS patients versus controls. SS patients exhibited slightly higher corneal temperature values immediately after eye opening than control subjects (35.07±0.4 οC vs 34.7±0.6 οC in SS and control eyes, p=0.057) ; they also showed a more pronounced mean temperature[BMC1] reduction along the interblink period (-1.65±0.7οC vs -1.46±0.5οC in SS and control eyes, p=0.393, Student t-test) but differences do not reach the significance level. In contrast, the slope of temperature decay (-0.204±0.2 οC/s vs - 0.105±0.050οC, p<0.05) was significantly faster in SS patients. Pearson correlation analysis showed a negative correlation between Schirmer test values and the slope of the temperature drop during the interblink period (correlation coefficient=-0.525; p<0.025).
Conclusions :
The faster reduction of corneal surface temperature during the interblink period in SS patients and its correlation with the tearing rate suggests a higher rate of tear evaporation. The rapid decrease of corneal temperature is expected to evoke a more pronounced activation of corneal cold thermoreceptors, which may contribute to the discomfort sensations experienced by dry eye patients.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.