Abstract
Abstract: :
Purpose: This study investigated whether tear break-up over the corneal surface is associated with increased dry eye symptoms and if tear break-up provides a stimulus for the blink following extended eye opening. Methods: Dry eye symptom questionnaires were completed by 17 dry eye (DE) and 11 normal (N) subjects. Following the instillation of fluorescein, subjects were instructed to hold one eye open for as long as possible while tear break-up was videotaped. This procedure was performed 3 times per eye, and subjects filled out the McGill Pain Questionnaire (MPQ) after each trial. Following all testing, subjects filled out a post-testing symptom questionnaire. Digitized videos were used to generate maps quantifying the total area of break-up (TBU) over the corneal surface by the intensity of tear film fluorescence. Results: There was a significant difference (p=0.003, t-test) in the time that subjects could hold their eyes open (maximum interval between blinks, MIBB) between DE (AVG:18 sec; SD:5 sec) and N (AVG:26 sec; SD:21 sec) subjects. The TBU was significantly greater (p=0.040, t-test) in DE (AVG:21%; SD:14%) than in N (AVG:9%; SD:7%) subjects. There was a significant correlation between the TBU and symptom frequency scores (r=0.456; p=0.011) and between eye comparisons of the MIBB (r=0.625; p<0.0001) and the TBU (r=0.875; p<0.0001). Dry eye subjects showed significantly higher symptom intensity scores than N subjects (p=0.002, t-test). More than 50% of subjects chose stinging on the MPQ to describe the discomfort associated with holding the eyes open. Conclusion: Holding the eyes open as long as possible caused tear break-up in all subjects and was associated with an increased level of dry eye symptoms in both DE and N subjects. The descriptor, stinging, may signify hypertonic conditions in areas of tear break-up on the corneal surface. The high correlation in the TBU between eyes implies that there is an individual threshold for tear break-up as a stimulus for the blink. Dry eye subjects had a more extensive TBU before blinking, which suggests a higher threshold for the blink, perhaps due to desensitization following repeated episodes of tear break-up on the corneal surface.
Keywords: 376 cornea: tears/tear film/dry eye • 430 imaging/image analysis: clinical