Contact lens lipid spoliation of hydrogel and silicone hydrogel lenses

The purpose of the study was to measure contact lens lipid spoliation of silicone hydrogel PureVision (balafilcon A) and hydrogel Acuvue 2 (etafilcon A) contact lenses worn for 10 hours single use (DD) and 7 days of extended wear (EW).

Two similar study populations (DD, n = 55; EW, n = 53), were enrolled at four study sites. In each population, a bilateral, randomized, crossover (lens material), subject-masked experimental design was followed. Worn contact lenses were analyzed for lipid uptake using high-performance liquid chromatography by two laboratories: Alcon Laboratories (right lens total uptake) and OTG Research & Consultancy (left lens total uptake and individual lipid classes).

Lipid uptake was different for the two materials: total lipid (p < 0.007), cholesterol esters (p < 0.001), cholesterol (p < 0.001 EW only), and triglycerides/phospholipids (p < 0.001) were higher for balafilcon A, whereas fatty acid (p < 0.0025 EW only) was higher for etafilcon A. The ratio of the extracted lipids was also different: higher percentages of triglycerides/phospholipids (p < 0.001) and cholesterol (p < 0.001 EW only) for balafilcon A and higher percentages of fatty acids/di- and monoglycerides (p < 0.014) for etafilcon A.

Total lipid uptake was highly material dependent. Both laboratories measured a greater uptake of lipids by the silicone hydrogel than the hydrogel material, a difference that was evident after only 10 hours of DD. Total lipid uptake was greater after 7 days of EW compared with 10 hours of DD. Of interest for contact lens spoliation and its avoidance was the differential lipid uptake profile, indicating material selectivity. Whereas greater differentiation between materials was possible after 7 days of EW for each material, the lipid uptake profile was similar for DD and EW, indicating a greater material effect than a wear modality effect.