An improved fluorophotometric method for tear turnover assessment

Scanning fluorophotometry is considered the "gold standard" to determine tear turnover rates (TTR). In this study, we attempted to improve the precision of basal TTR by fluorophotometry through a number of methodological changes. By means of a timer program that produces audio cues, a new methodology that ensures confluence and a constant thickness of the tear film and minimization of reflex lacrimation as a result of the inhibition of the blink reflex was developed. This was compared with the standard protocol, both in a paired study and by a review of unpaired data. The minimum length of time required to monitor TTR measurements was also investigated. A significant improvement in correlation coefficient (r) of the log decay curve was observed as a result of changes in the protocol in both the paired (p = 0.016) and unpaired study (p <0.0001). We determined that it was sufficient to monitor TTR for 10 min to obtain accurate results. We advocate that the changes be adopted as widely as possible for the precise and rapid measurement of basal tear turnover rates.