Do contact lens solutions stand the test of time? : Part 1: The "aging" of lubricants

Abstract

For some patients, use of lubricant colutions is essential for achieving successful contact lens wear. Matchiing solution actions to the needs of the patient is most typically achieved through trial and error, although those actions must be intimately related to the inherent chemical and physical properties of the lubricants.(1-2) But assuming an effective choice of lubricant has been made, how certain can we be that those same needed properties will be maintained throughout its use? Can changes in those properties occur, sufficiently marked as to cause a significant reduction in or loss of effectiveness? We have explored this potential for instability using a sample of eight lubricant solutions. Four properties - pH (or acidity), buffering capacity, tonicity and refractive index - were measured at two times, immediately on opening, and then after 24 months of subsequent storage.