Am J Ophthalmol. 2006 Apr;141(4):758-60.   

McCulley JP, Aronowicz JD, Uchiyama E, Shine WE, Butovich IA.  Department of Ophthalmology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 

PURPOSE: To establish scientific relationship between relative humidity (RH) and aqueous tear evaporation to elucidate possible significance of this relationship in normals and aqueous tear deficiency patients.  

DESIGN: Prospective experimental laboratory study.  

METHODS: Ocular surface evaporation was determined using evaporometry and calculated for two ranges of RH, 25% to 35%, and 35% to 45% in a randomized clinical patient population.  

RESULTS: Average evaporative rate in the higher humidity range was between 0.029 +/- 0.009 through 0.043 +/- 0.016 mul/cm(2)/min. At lower humidity, range was between 0.044 +/- 0.013 through 0.058 +/- 0.018 mul/cm(2)/min. Differences in the corresponding evaporative rates were statistically significant (between P < .003 through P < .043) for each analysis.  

CONCLUSIONS: A decrease of 10% RH resulted in an average difference of between 28.33% to 59.42% increase in evaporation. The increase in evaporation at lower humidity has significant clinical implications for patients with aqueous deficient dry eyes, and possibly those undergoing laser-assisted in situ keratomileusis (LASIK).