Objectives: To evaluate the performance of the dynamic-area high-speed videokeratoscopy technique in the assessment of tear film surface quality with and without the presence of soft contact lenses on eye.
Methods: Retrospective data from a tear film study (Kopf et al., J Optom. 2008;1:14-21) using basic high-speed videokeratoscopy, captured at 25 frames per sec, were used. Eleven subjects underwent tear film analysis conducted in the morning, midday, and evening on the first and seventh day of 1 week of no lens wear. Five of the 11 subjects then completed an extra week of hydrogel lens wear, followed by a week of silicone hydrogel lens wear. Analysis was performed on a 6-sec period of the interblink recording. The dynamic-area high-speed videokeratoscopy technique uses the maximum available area of Placido ring pattern reflected from the tear interface and eliminates regions of disturbance because of shadows from the eyelashes. A value of tear film surface quality was derived using image-processing techniques based on the quality of the reflected ring pattern orientation.
Results: The group mean tear film surface quality and the standard deviations for each of the conditions (bare eye, hydrogel lens, and silicone hydrogel lens) showed a much lower coefficient of variation than that of previous methods (average reduction of approximately 92%). Bare eye measurements from the right and left eyes of 11 individuals showed high correlation values (Pearson correlation r = 0.73, P<0.05). Repeated measures ANOVA across the 6-sec period of measurement in the normal interblink period for the bare eye condition showed no statistically significant changes. However, across the 6-sec interblink period with both the contact lenses, statistically significant changes were observed (P<0.001). Overall, wearing hydrogel and silicone hydrogel lenses caused the tear film surface quality to worsen compared with that of the bare eye condition (repeated measures ANOVA, P<0.0001 for both the hydrogel and silicone hydrogel).
Conclusions: The results suggest that the dynamic-area method of high-speed videokeratoscopy was able to distinguish and quantify the subtle, but systematic worsening of tear film surface quality in the interblink interval in contact lens wear. It was also able to clearly show a difference between bare eye and contact lens wearing conditions.