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George W. Ousler, III, Patrick Johnston, Donna Welch, Keith J. Lane, Mark B. Abelson; Validation of the Enhanced Controlled Adverse Environment II. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3857.
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The Controlled Adverse Environment II (CAE) aims to standardize the study of dry eye in a controlled reproducible environment that challenges the eyes of all patients equally and for the same amount of time. The model exacerbates dry eye signs and symptoms by regulating humidity, temperature, airflow, and lighting conditions. The purpose of the study was to demonstrate the validity, repeatability, and reproducibility of the CAE for assessing ocular discomfort and average corneal staining over inferior, central, and superior regions.
Retrospective analysis was based on sign and symptom data from 600 dry eye subjects from the last 4 CAE studies conducted at Ora. Specific endpoints were ocular discomfort (0-4 in unit increments), and average corneal staining over inferior, central, and superior regions (0-4 in half-unit increments). In each study, untreated subjects were exposed to the CAE for 90 minutes at two consecutive visits one week apart. The effect of the chamber was based on pre and post-chamber means at Visits 1 and 2, and the differences between post-chamber means across these visits. These quantities were calculated for each study, and combined differences were calculated as a weighted average of study differences. 95% confidence intervals (CIs) were used to compare post-pre differences between studies.
Exacerbating effects on means were repeated across visits. For corneal staining, pre and post-chamber means were 1.49 and 2.22 for Visit 1, and 1.49 and 2.25 for Visit 2, giving post-pre differences of 0.73 and 0.76, respectively. For ocular discomfort, pre and post-chamber means were 1.77 and 3.13 for Visit 1, and 2.03 and 3.21 for Visit 2, giving post-pre differences of 1.36 and 1.17, respectively. These post-pre differences were reproducible across studies. For corneal staining, the 95% CI for the difference between visits was (-0.01, 0.08) for the combined sample, and individual study CIs were within ± 0.22. For ocular discomfort, 95% CIs were (0.01, 0.16) for the combined sample, and were within ± 0.29 for all studies.
CAE validity and repeatability were demonstrated for the combined sample. These attributes were shown to be reproducible across the 4 individual studies.
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