Osmolality and buffering agents in soft contact lens packaging solutions

Area of Science:

• Ophthalmic research
• Biomaterials science
• Contact lens technology

Background:

• Soft contact lenses are medical devices requiring precise manufacturing and packaging.
• Packaging solution properties, including osmolality and buffering agents, are critical for maintaining lens integrity.
• Variations in lens parameters can affect visual acuity and patient comfort.

Purpose of the Study:

• To investigate the influence of packaging solution osmolality and buffering agents on key soft contact lens parameters.
• To assess whether these factors cause lens parameters to deviate from nominal values and established tolerances.

Main Methods:

• Selected soft contact lenses from different FDA material categories were equilibrated in phosphate-buffered saline (PBS) or borate-buffered saline (BBS).
• Solutions were adjusted to three osmolality levels (270, 310, 414 mOsmol/kg).
• Lens diameter (LD), base curve (BOZR), and back vertex power (BVP) were measured and compared to labeled values.

Main Results:

• All measured lens parameters (LD, BOZR, BVP) showed statistically significant changes across varying osmolality and buffering conditions.
• Etafilcon A, alphafilcon A, and balafilcon A exhibited greater parameter alterations than lotrafilcon A.
• Specific lenses, including alphafilcon A (LD) and lotrafilcon A/etafilcon A (BVP), deviated beyond ISO tolerance limits when tested in simulated packaging solutions.

Conclusions:

• Packaging solution osmolality and buffering agents demonstrably influence soft contact lens parameters.
• The findings indicate that packaging solution composition can lead to deviations in lens parameters, potentially exceeding international standards.