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A. Salapatek, F. Soong, D. Wilson, L. Pozza, P. Patel; Validation of a Clinical Model to Study Dry Eye Syndrome (DES) in a Controlled Low Humidity Environment (LHE) Chamber. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3666.
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The challenge in studying DES is that signs and symptoms vary substantially between patients and result in variable outcomes depending on environment, time and tasks. Large patient numbers are typically required for drug testing in the field. The objective was to develop and validate a controlled LHE chamber model for the clinical investigation of ocular therapeutics, devices and DES etiology.
The LHE chamber is a state-of-the-art environmental exposure facility designed to maintain temperature (19-25ºC), RH≤10% and apply dry air to patients at levels similar to arid regions (velocity 5ft±3ft/s). 48 patients were enrolled in this study that included a placebo run-in period between two 90min LHE chamber visits (V1&V2) with minimum inter-visit interval of 1wk. Enrollment criteria included: OSDI score ≥31.25; corneal & conjunctival staining sum score ≥1 (Oxford scale) and ocular burning or stinging score ≥1 (0-4 scale). Conjunctival redness, corneal & conjunctival staining, Schirmer test, and TBUT were measured pre and post-chamber exposure. Ocular symptom scores of photophobia, blurred vision, grittiness/sandiness, painful/sore, burning or stinging sensations were recorded on diary cards at designated intervals during chamber visits.
Environmental conditions in the LHE were validated to be temporally and spatially uniform within targeted tolerances. At V1&V2, there was a significant reproducible increase in corneal & conjunctival staining (Mean change from baseline: V1:4.15±0.19;V2:3.97±0.23) and a decrease in TBUT (V1:-3.00±0.51;V2:-3.31±0.81). No significant changes in conjunctival redness nor Schirmer’s were noted. At V1&V2, symptoms were exacerbated consistently throughout visit duration with maximization by 1h. The time-course of symptom development was similar at both visits with a trend for mean symptom sum of V2<V1 (V1:11.87±4.19;V2:10.43±5.38).
The LHE chamber is validated to maintain stable and repeatable environmental exposures which exacerbate ocular signs and symptoms of DES. Key ocular measures of corneal & conjunctival staining and TBUT show reproducibility. Reduction of symptom scores upon LHE re-exposure suggests patient accommodation must be considered. The LHE chamber model provides a valuable and important clinical research option for the study of DES.
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