Abstract
Purpose :
The purpose of this investigation was to examine the volume effect of common clinical tear breakup time (TBUT) methods, and to evaluate test efficacy in an independent sample, both samples free of selection bias.
Methods :
All subjects were evaluated using a battery of standard dry eye tests except TBUT. Efficacy study: Subjects were randomized to the Dry Eye Test (DET), Standard Strip (SS) and 2.0 microliters of 1.0% NaFl, on separate days. A masked examiner measured TBUTs from video recordings. Verification study: Subjects were analyzed, using NaFl volumes of 5.0 microliters of 2.0% and 2.0 microliters of 1.0% NaFl for TBUT. Raw values were log transformed prior to analysis. Cross validation was undertaken for efficacy and cut-point predictive ability by splitting the verification data.
Results :
Efficacy study: 15 normals, and 31 dry eye subjects completed the study. Log-transformed TBUTs were all significantly different, normals vs. drys, for all 3 methods (all p values < 0.001). AUCs, cut-points, sensitivity and specificity were: 1) DET, 0.873, 4.4 secs, 0.97 and 0.67, respectively, 2) 2.0 microliters: 0.901, 3.22 secs. and 0.90 and 0.87, respectively, and 3) SS: 0.912, 3.42 secs, and 0.97 and 0.80, respectively. Verification study: There was no difference between the dry and normal eye TBUTs for the two NaFl volumes, so the data were combined providing 142 drys and 90 normals. Of these, ~70% were used for model building with the remainder for model checking. This resulted in an AUC of 0.81, cut-point of 5.31 secs, with sensitivity 0.78 and specificity 0.75. Predictive accuracy was 67% and 76% for normals and drys, respectively.
Conclusions :
Little difference in TBUT was found using the three clinical methods, although TBUTs were short, due to the video recording approach. Test efficacy using liquid NaFl suggests that the TBUT test has acceptable diagnostic accuracy.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.