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S. Jalal, J. Wang, S. Ching, S. Chung; Central Tear Film Thickness Before and After Blinks . Invest. Ophthalmol. Vis. Sci. 2006;47(13):265.
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The tear film is renewed with each blink. The impact on the tear film thickness by blinking remains unknown. The aim was to determine central tear film thickness before and after blinks using real time corneal optical coherence tomography (OCT).
Custom built corneal OCT was developed to obtain rapid repeated cross–sections of the tear film over the cornea. Eight healthy subjects with no history of dry eye were recruited into this study. Both eyes were imaged with a vertical 12.5mm OCT scan at 8 images per second. Eight images were obtained immediately before and after five consecutive blinks. A total of 5 blinks and 4 blink intervals were analyzed for each subject using custom software.
After each blink, tear film thickness increased an average of 3.2 microns (SD= 2.63) compared to the thickness immediately before the blink (paired t–test, p=0.002). After eye opening, tear film thickness decreased an average of 2.9 microns (SD=3) compared to the thickness immediately after eye opening (paired t–test, p=0.004). Eyes with higher increases of the tear film after blinks showed higher decreases between blinks.
This is the first study examining the effect of blinking on tear film thickness. The data showed that blinking thickens the tear film and that eye opening thins it. The method developed in this study appears to be a promising method to study the tear film system.
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