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JP Varikooty, T Simpson, L Jones, D Fonn; Ocular Discomfort during Tear Film Drying . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3106.
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Purpose:To find the relationship between tear film drying and sensation during the inter-blink period Methods:Software written using MATLAB sampled a slitlamp video camera at 4Hz, a potentiometer and a microphone at 10 KHz. One eye was taped shut and after a blink, the subjects were required to keep their other eye open. Digital video images of the ocular surface (with fluorescein) were obtained using a slit lamp biomicroscope. Twenty two subjects rated the intensity of the ocular surface sensation by adjusting a 1-turn potentiometer to represent the strength of the discomfort. They were trained to use the potentiometer before the data were collected. In addition, the characteristics of the sensation as spoken by the subject were recorded. The extent of drying (dark pixels) on the cornea was assessed with a macro written in Object-Image 2.08 software. Results:Our previous work has shown that sensation was generally biphasic with initial discomfort increasing slowly (mean slope 0.70±0.12) followed by a rapid increase (mean slope 5.0±0.4) lasting perhaps 2 seconds before subjects blink (Varikooty, et al. IOVS 42(4): S941-S941,2001). For all data sets, the tearfilm drying was linearly correlated to time with a median correlation coefficient of 0.88. This was improved using power functions to 0.97. The median linear correlation between extent of drying and ratings of discomfort was 0.81 and this could be improved to 0.92 with up to 3rd order polynomials. Conclusion:Our method provides novel information about the development of discomfort during ocular surface drying. As evidenced by the polynomial functions required to adequately describe the relationships, tear film drying and ocular surface sensations are associated in complex ways. Further studies are needed to elucidate the relationship between the ocular surface drying and discomfort and the variety of tear film rupture patterns.
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