Osmolality and buffering agents in soft contact lens packaging solutions.

The study determined the effects of packaging solution osmolality and buffering agent on soft contact lens parameters. One lens type from each FDA contact lens material category was equilibrated to phosphate buffered saline (PBS) or borate buffered saline (BBS), at three osmolality concentrations: 270, 310 and 414 mOsmol/kg. Lens diameter (LD), base curve (BOZR) and back vertex power (BVP) were measured and compared to nominal packaging label values. Statistically significant differences were found in all three parameters across all osmolality levels for both buffering agents. Etafilcon A showed the largest amount of parameter change, followed by alphafilcon A and balafilcon A. Lotrafilcon A was the least affected. LD of alphafilcon A lenses (greater than +/- 0.2 mm) and BVP of lotrafilcon A and etafilcon A lenses (greater than +/- 0.25 D) measured outside the International Standards Organization (ISO) tolerance from their packaging labels when measured in solutions that mimicked their packaging solutions. Osmolality and buffering agents influence lens parameters. Packaging solutions can vary the parameters of some lens types from their nominal value to outside the tolerance range set by ISO.