USE OF HIGH-SPEED, HIGH-RESOLUTION THERMOGRAPHY TO EVALUATE THE TEAR FILM LAYER

PURPOSE: To evaluate the tear film layer in patients with dry eye and in normal subjects by measuring the corneal temperature with infrared radiation thermography. METHODS: One eye of each of 13 patients with d ry eye and one eye of each of seven normal subjects were evaluated ran domly. The corneal temperature was measured continuously with a recent ly improved infrared radiation thermography technique. We calculated t he k value, which reflected the steepness of the corneal temperature c hange. The bigger the k value was, the mote rapid was the decrease in corneal temperature, and this was directly related to increased evapor ation. RESULTS: With normal blinking, the mean k value for patients wi th dry eye (5.6 +/- 2.9 per second) was significantly less than that i n the control subjects (9.3 +/- 5.0 per second; P < .05). Keeping the eyes open after closing the eyes significantly decreased the k values compared with normal blinking in both groups (P <.05). CONCLUSIONS: Ou r findings demonstrate the usefulness of this method of measuring corn eal temperature to evaluate the tear film layer. Highspeed, high resol ution thermography detected sub tie changes in corneal temperature wit h enhanced sensitivity and spatial and temporal resolution. We found t hat the mean k value, and therefore the rate of decline in corneal tem perature in patients with dry eye, was significantly less than that in normal subjects. The k value may therefore reflect tear film layer st ability. The measurement of the changes in the corneal temperature can thus give us valuable information on the tear film layer.