Abstract
Purpose: :
Contact lens manufacturers employ surface coatings and surface-modifying end groups to mask the hydrophobic nature of the bulk lens. We investigated the degree to which hydrophobic domains on the surface and in the bulk of the lens can be imaged over periods of in vitro and in vivo wear. The effect of multipurpose solutions (MPS) on lens hydrophobic domains was also investigated.
Methods: :
Four types of silicone hydrogel lenses (Acuvue Oasys, Acuvue Advance, PureVision, and O2Optix) were exposed to artificial tear fluid (ATF) or worn for a day and then tested for hydrophobic domain staining. Hydrophobic domain staining was determined using a saturated solution of Sudan IV. Staining was measured by photography and total amount of dye adsorbed.
Results: :
Specific differences in staining were found for all control lenses. ATF exposure and wear significantly decreased the staining response for all lens types (p = 0.001). However, the trend of staining remained the same: PureVision > Acuvue Advance > Acuvue Oasys > O2Optix. The pattern of staining was specific for each lens type. While MPSs also decreased staining, the extent of their effect varied with lens type.
Conclusions: :
Hydrophobic staining of lenses visualized domains on and within silicone hydrogel lenses. Differences in staining response after exposure to ATF, MPS, and wear indicate the potential for increased protein and lipid deposition on the different lens types and the possibility of MPS to block that deposition. Hydrophobic staining techniques may be useful for determining differences in surface modification techniques and biofouling of silicone hydrogel lenses.