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B. J. Straker, M. Kopf, F. Yi, R. Iskander, M. J. Collins; Dynamic Videokeratoscopy and Tear Surface Quality With Soft Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4830.
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The aim of this study was to investigate changes in tear film surface quality after commencing soft contact lens wear.
Tear film surface quality was assessed using dynamic videokeratoscopy with a modified Medmont E300 videokeratoscope. Reflected images of the Placido disk are captured at 25 frames per second during the interblink period. A quantitative value of tear surface quality is derived for each frame, based on image processing analysis of the raw Placido ring images (not the derived topography). Eleven young subjects participated in the study. They were screened to ensure that their tear characteristics were within normal limits. Dynamic videokeratoscopy measurements were taken three times per day; in the morning (8-10 am), at lunchtime (12-2 pm), and in the afternoon (4-6 pm). This was done on two baseline days (bare eye) and on the first and seventh days of lens wear for a conventional hydrogel lens and following a week of no lens wear, for a further week of silicone hydrogel lens wear. Additional tests to assess the tear film were also conducted and each subject was asked to rate (analogue scale) the subjective dryness of their eyes.
All lens wear measurements showed a significant worsening of the tear film surface quality compared to bare eye baseline measurements (repeated measures ANOVA, p<0.01). A significant diurnal change was found on the first day of silicone hydrogel contact lens wear, where the tear film surface quality improved during the day (p=0.045). However, no diurnal changes were found in the tear film surface quality for the other lens wearing days or for the baseline bare eye condition (p>0.05). The subjective rating of dryness correlated with tear surface quality values for the bare eye condition (Pearson's p=0.04) and approached significance for the lens wearing conditions (hydrogel p=0.13 and silicone hydrogel p=0.21).
The measurement of tear film surface quality using dynamic videokeratoscopy does differentiate between bare eye and lens wearing conditions. It also shows a systematic improvement in tear surface quality during the first day of silicone hydrogel lens wear.
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