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A. Tomlinson, S. Khanal; Effectiveness of Tear Physiology Tests in the Differential Diagnosis of Dry Eye Subtypes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5852.
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In a previous study we have shown tests of tear physiology to be the most effective in the diagnosis of global dry eye. This study aims to determine the effectiveness of tear physiology tests in the differential diagnosis of aqueous deficiency dry eye (ADDE) and evaporative dry eye (EDE).
Fifty six dry eye patients were classified into 30 ADDE and 26 EDE according to the recently published dry eye workshop criteria. A range of tear physiology measures including tear evaporation, turnover rate (TTR), distribution, volume and osmolarity and meibomian gland dropout (MGD) were assessed on these patients. Effectiveness of the tests, singly and in combinations, in differentiating between these subtypes was evaluated by retrospective allocation into groups and Receiver Operative Characteristics (ROC) curves.
Statistically significant differences were seen for TTR and tear evaporation and no significant differences were seen for tear osmolarity, volume, distribution and meibomian gland dropout scores between ADDE and EDE. A cut-off value of 11%/min for TTR was found to have a sensitivity of 86%, specificity of 75%, positive predictive value (PPV) 89%, negative predictive value (NPV) 69% and overall accuracy (OA) 83% in the differentiation of ADDE and EDE and the area under the curve on the ROC curve was 0.83. Similarly, tear evaporation, with a cut-off of 60 g/m2h, was found to have a sensitivity of 77%, specificity of 55%, PPV 38%, NPV 80% and OA 58% with an area under the curve of 0.59 on the ROC curve. From the histogram of the evaporation rate of ADDE and EDE, an overlap coefficient of 0.76 was found indicating that tear evaporation is within a similar range in these two dry eye subtypes.
TTR can be used to differentially diagnose ADDE from EDE. There is no clinically significant difference in the tear evaporation between these two primary dry eye subtypes.
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