Tear pH and the soft contact lens patient

Abstract

Already soft contact lenses of certain materials have reported to be dimensionally sensitive to the pH of their surroundings. For example both water content and diameter may become measurably reduced as the lens environment becomes more acidic. Such observations, of course, tend to raise certain clinical questions. What exact range of tear pH is a new soft lens likely to encounter when first dispensed, and may that range commmonly exceed the stability limits of the material, as verafied by the manafacturer? Is it possible, too, that over the longer term as the patient adapts and increase the wearing time, the lens might induce an acid shift in the tears (eg. by the lens acting as a reservoir for the acid by products of corneal metabolism)?