Abstract
Purpose: :
Silicone hydrogels were initially commercialised 10 years ago to improve oxygen transmissibility to the eye. Since then, many modifications to the bulk and surface properties of the lenses have been undertaken to improve the wettability and comfort of the lenses. Recently, manufacturers have incorporated various surface active agents into the blister packaging solutions (BPS) of the lenses to improve initial comfort of the lens on eye. The purpose of this study was to measure and compare the physical properties of the BPS for 9 silicone hydrogel lenses, 2 conventional polyHEMA-based hydrogel lenses, and 2 saline control solutions.
Methods: :
The pH, surface tension (ST), viscosity, and osmolality of the BPS was measured for lotrafilcon A, lotrafilcon B, and lotrafilcon B with a "modified BPS" (m-lotrafilcon B) (CIBA Vision, Duluth, Georgia), balafilcon A (B&L, Rochester, New York), galyfilcon A, senofilcon A and narafilcon A (Johnson & Johnson, Jacksonville, Florida), and comfilcon A and enfilcon A (CooperVision, Pleasanton, California) and BPS from two conventional polyHEMA-based materials - etafilcon A (Johnson & Johnson, Jacksonville, Florida) and omafilcon A (CooperVision, Pleasanton, California). The two saline solutions examined were Unisol (Alcon, Fort Worth, Texas) and Softwear Saline (CIBA Vision, Duluth, Georgia).
Results: :
The pH results for all BPS remained in the pH range of tears (6.6-7.8). The ST of the modified BPS was significantly lower (p<0.01) than the original non-modified BPS. Viscosity measurements ranged between 0.90-1.00cP for all BPS except for the modified BPS, which had significantly higher viscosities (p<0.001). Osmolality measurements were not significantly different (p>0.05) between BPS made by the same manufacturer but were significantly different comparing BPS made by different manufacturers (p<0.05).
Conclusions: :
The incorporation of surface active agents into BPS can alter the physical properties of the BPS of silicone hydrogel lenses and warrants investigation into their initial wettability and comfort of the lens on eye.
Keywords: contact lens • pH • cornea: tears/tear film/dry eye