This study examines the stability and range of pH in several commercially available artificial tear preparations. pH immediately upon opening varies between 6.4 and 8.5 among the preparations. pH fluctuation was not found to occur in five of the seven preparations. The pH of one lot of a multiple use artificial tear decreased 0.4 units during the first week and then remained stable for the following 21 days. pH was found to vary by 0.5 units between lots in one brand of a single use artificial tear preparation. These results allow for informed selection of artificial tears in the treatment of dry eye.
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