The article below discusses the "washout effect"
Evaluation of the Frequency of Ophthalmic Solution Application
"Even a single application of saline solution resulted in significant changes in major tear protein and sialic acid concentration in the tears of normal subjects."
http://www.ncbi.nlm.nih.gov/pubmed/23521663
Evaluation of the Frequency of Ophthalmic Solution Application
"Even a single application of saline solution resulted in significant changes in major tear protein and sialic acid concentration in the tears of normal subjects."
http://www.ncbi.nlm.nih.gov/pubmed/23521663