Purpose: In the tear film lysozyme makes up approximately 35% of the total protein detected and is widely implicated in contact lens spoilation. It functions primarily as a bacteriolytic enzyme in the innate defense of the ocular surfaces. Recently interest in this protein has focused on its ability to function effectively in the presence of contact lens and care solution products. Method: The classic methods based on its interaction with, and the lysis of, the Grampositive bacterial strainMicrococcus lysodeicticus,measured by turbidity at 450nm, were used to investigate lysozyme antimicrobial activity. In addition a fluorescence-based assay which measures the digestion products from a DQTM lysozyme substrate, with excitation maxima at 494nm and fluorescence emission maxima at 518nm, was assessed. Results: Disadvantages of turbidity based assayswere apparent. Additionally many studies use egg white lysozymes as a cheaper assay alternative to human sourced protein, but in addition to compositional variation, human and chicken lysozymes differ in enzymatic activity with a 4:1 ratio respectively. Batch to batch variation in lysozyme preparations was also observed. The kinetic fluorescencebased assaywhich was able to detect activity down to 20U/ml was established and was used to assess the effects that extraction techniques and sample preparation have on the outcome of the activity data. Conclusions: An investigation into the true nature and extent of lysozyme denaturation, which is essential to determine the importance of this phenomenon and its impact on tear film anti-microbial function, was facilitated by more sensitive and varied analytical techniques.