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D. Alonso-Caneiro, R. Iskander, M. J. Collins; Dynamic-Area High Speed Videokeratoscopy for the Assessment of Tear Film Surface Quality. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6348.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of this study was to assess an enhanced high speed videokeratoscopy method to quantify tear film surface quality.
Tear film surface quality was assessed using an image processing based methodology in which the area of analysis is maximized to cover the corneal surface, which is not affected by the shadows of eyelashes. This is followed by evaluation of the Placido disk pattern coherence over the area of analysis. The coherence analysis, which is a measurement of the consistency of the pattern’s local orientation, provides a quantitative value of the tear film surface quality. Data from retrospective dynamic videokeratoscopy measurements in eleven subjects wearing hydrogel and silicone hydrogel lenses were used to assess the tear film surface quality during an inter-blink period. The study was conducted over a four week period. In the first week bare eye measurements were taken. This was followed by a week of conventional hydrogel lens wear. No measurements were conducted in the third week and subjects did not wear contact lenses. In the fourth and final week subjects wore a silicone hydrogel lens. Measurements were taken in the first and seventh day of each week, three times per day; in the morning, at lunchtime, and in the afternoon.
Bare eye measurements from the right and left eye of the same individual showed significant high correlation (Pearson’s r=0.835, p<0.05). All bare eye measurements showed significantly higher (better) values of the tear film surface quality compared to contact lens on eye measurements (repeated measures ANOVA, p<0.001). Additionally, all lens wear measurements showed a significant trend of worsening of the tear film surface quality values over the inter-blink interval of measurement (repeated measures ANOVA, p<0.001) as compared to bare eye baseline measurements that showed a relatively flat trend in the inter-blink interval. Time of the day and week did not produce significantly different results in tear film surface quality.
This method can differentiate between tear surface quality for bare eye and lens on eye conditions. It can also show the subtle, but systematic worsening that the lens on eye creates during the inter-blink period of measurement.
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