Comparing the extent of protein build-up on several disposable lenses by two spectrophotometric methods

Preservation of human tear protein structure and function by a novel contact lens multipurpose solution containing protein-stabilizing agents

OBJECTIVES

Tear film proteins have antimicrobial and other functions that may be lost after denaturation during contact lens wear. A new multipurpose solution has recently become available (Biotrue, Bausch + Lomb Inc., Rochester, NY), which contains protein-stabilizing agents including hyaluronic acid, poloxamine, and sulfobetaine 10, the latter used previously as a laboratory tool to renature proteins. We examine whether this new multipurpose solution formulation can prevent the denaturation of human lactoferrin and lysozyme at physiologic levels in response to a powerful denaturing challenge.

METHODS

Human lactoferrin and lysozyme were treated with sodium dodecyl sulfate (SDS) either with or without an investigational version of the new multipurpose solution (without its two disinfectant agents) (investigational multipurpose solution [iMPS]). The structure was assessed by native-polyacrylamide gel electrophoresis (PAGE), differential scanning calorimetry (DSC), and fluorometry; additionally, antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus was measured.

RESULTS

The iMPS prevented an SDS-induced shift in the native-PAGE banding position of lactoferrin. The SDS treatment substantially altered the lactoferrin DSC and fluorescence spectra, indicating that the protein had denatured. This change did not occur in the presence of iMPS. Lactoferrin and lysozyme showed antibacterial and bacteriolytic activity, which was abolished after SDS treatment; this loss of activity did not occur for proteins treated with iMPS.

CONCLUSIONS

These data clearly show that the iMPS prevents the denaturation of physiologic levels of human lactoferrin and lysozyme by the strongly denaturing surfactant SDS and that stabilized proteins retain their function. We conclude that this solution has the capacity to stabilize the structure and function of tear proteins.

Overwear of contact lenses: increased severity of clinical signs as a function of protein adsorption

This study compared the clinical behavior of disposable and frequent replacement Acuvue and 1-Day contact lenses. Each type of lens was worn on one eye according to the schedule recommended by the manufacturer, and on the other eye for a longer period of time, up to 30 days in length. Both type of lenses were prescribed on a daily-wear basis. The amount of protein collected from the lenses was measured using two spectrophotometric protein assays. Visual acuity and comfort, along with several other clinical signs, were classified according to Cornea and Contact Lens Research Unit (CCLRU) scales, and possible associations between each of these signs and the amount of protein extracted from the lenses was tested. A comparison between the lens worn on the compliant eye with the lens worn on the noncompliant eye allowed us to measure the impact of overwear on ocular health and subjective clinical findings. After four months of study, the overwear of Acuvue and 1-Day lenses significantly increased the amount of protein bound on the contact lenses, as well as the severity of upper conjunctival papillae, upper lid conjunctival hyperemia, and limbal congestion. Even if reduced values for visual acuity and noninvasive break-up time (NIBUT) were identified, these variations were not found to be statistically significant. The clinical implications of this study would allow a practitioner to identify, according to the variations in several clinical signs, a patient who overwears contact lenses, so that action may be taken to reduce possible deleterious effects on ocular health.