Exposure to a controlled adverse environment impairs the ocular surface of subjects with minimally symptomatic dry eye

PURPOSE. Adverse environmental conditions elicit dry eye ( DE) related signs and symptoms. The purpose of this work is to determine whether these conditions can alter a normal-toborderline ocular surface in subjects with DE symptoms. METHODS. Ten minimally symptomatic contact lens ( CL)-wearing subjects were exposed, without (WO-) and with (W-)CLs, to a controlled adverse environment (CAE) of 22.0 +/- 2.0 degrees C and 19.0% +/- 4.0% relative humidity ( RH) for 2 hours in an environmental chamber (EC). One month later, the same subjects were placed in an indoor normal environment (INE) of 24.2 +/- 1.3 degrees C and 34.8% +/- 2.9% RH for 2 hours. DE-related signs and symptoms were evaluated before and after each exposure. The reversibility of changes provoked by CAE or INE was also evaluated. RESULTS. Without CL wear, significant changes were found in DE signs (noninvasive tear break-up time [NIBUT], conjunctival hyperemia and phenol red thread test) after CAE exposure, but not found after INE exposure. However with CL wear, the same tests were altered after both CAE and INE exposure. Most of these changes returned to normal values within 1 month after environmental exposure. CONCLUSIONS. Significant changes in comfort and the ocular surface tests were found after 2 hours of exposure to CAE. These results show the negative impact that an adverse environment, especially low RH, can have on the ocular surface. These alterations were fully reversible. This indicates that the CAE is a safe and functional condition in which to standardize DE diagnostic tests and evaluate therapeutics.