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E. I. Pearce, A. Tomlinson, L. C. McCann, S. B. Kaye, A. C. Fisher; A Clinical Alternative to Fluorophotometry for Measuring Tear Production in the Diagnosis of Dry Eye. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4674.
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To determine the utility of the Liverpool modification Tear Function Index (TFI) test in assessing tear production; evaluate association of tear clearance rate (TCR) and TFI with measurements of tear turnover rate (TTR) by fluorophotometry and determine effectiveness of these test in dry eye (DE) diagnosis.
Forty-one DE and fifteen control subjects participated. Tests carried out were; assessment of symptoms, fluorophotometry (by automated scanning fluorophotometer), Schirmer test and TCR and TFI with a commercial TFI strip.
Significant differences between DE and control subjects were found with all tests (p<0.05). DE subjects had lower values for all tests indicating reduced tear production. The best test for diagnosing DE was TTR with sensitivity (sens) 71%, specificity (spec) 60% and positive predictive value (PPV) 83%. As this test is not readily clinically available, associations between this and the other tests were determined. Significant correlations were found between TTR and Schirmer, TCR and TFI; indicating these clinical tests as potential surrogates for TTR by fluorophotometry. The strongest correlation found was between TTR and TCR at 0.69 (p=0.000) and TTR and TFI at 0.65 (p=0.000), indicating TCR or TFI can be used as an alternative to TTR by fluorophotometry in the diagnosis of DE. The agreement of the TTR and TCR measurements was confirmed by Bland and Altman analysis. The diagnostic effectiveness of these tests was compared, both TCR and TFI were found to be effective with sens, spec and PPV of 78%; 40%; 78% and 83%; 40%; 79% respectively.
The study demonstrates TCR measured by the commercially available Liverpool modification TFI strip is an appropriate alternative to TTR by fluorophotometry as a measure of tear production. It is also effective as a single test for the discrimination of those with DE from those without the condition.
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