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E. Angjeli, J. Rodriguez, K. J. Lane, M. B. Abelson, G. W. Ousler, III; Evaluation of Enhanced OPI; Using Computerized Video Tracking of Tear Film Break Up for Evaluation of Tear Film Stability. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3377.
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Fluorescein imaging of tear film break up time (TFBUT) remains a standard diagnostic for assessing dry eye disease. However, this one-dimensional, singular assessment is a poor representation of overall tear film mechanics. Clinically, normal and dry eye subjects present overlapping ranges impeding clear differentiation between the populations. Instead, better discrimination between normal and dry eye subjects may be best observed in the events following TFBUT. The rapid rate of tear film decay in dry eye subjects exposes large areas of the cornea to environmental factors compared to normal subjects. To better assess the integrity of the tear film it becomes necessary to quantify both the time and area the cornea remains protect after TFBUT. This concept led to the development of a "time-area" protection assessment of the tear film as it breaks up within the subject’s blink pattern under controlled visual task, functioning as an improved Ocular Protection Index (OPI).
Ten normal and ten dry eye subjects were video recorded for one minute OU in a one visit study. Inclusion was based on staining, symptoms, and a blink rate > 6 blinks/min. In order to carry out a real-time assessment of subjects’ OPI, a computer program was developed. Fluorescein imaging videos are input into the program and graphical output of time-area of tear covered cornea is produced.
Dry eye subjects had an average time-area protection of 95% ±4.7%; the normal population had coverage of 99.8% ±0.2% (p=0.0047). This means that, on average, dry subject expose about 5% of their corneal area to environmental factors, whereas subjects with stable tear film expose only about 0.2%.
This method of tear film assessment may be more clinically relevant and more precise then previous diagnostic techniques as it directly indicates the amount of corneal protection. The use of enhanced OPI may provide a more appropriate method to differentiate dry eye and non-dry eye subject populations, and evaluate potential therapeutic effects.
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