Defining Daily Disposable Contact Lens Wear in a Clinical Study

The U.S. Food and Drug Administration regulates contact lenses as prescription medical devices and defines daily disposable lenses for single use; however, safety comparisons between daily disposable and reusable lenses rely on the lens-wearing regimen. When inappropriately discerned, studies may erroneously report replacement regimen, resulting in inaccurate risk rates.

This study aimed to explore different measures for defining daily disposable wearers in the context of a clinical study.

A secondary analysis of data from five multisite fieldings (n = 1059) from the Contact Lens Risk Survey was performed. Descriptive statistics were used to examine self-reported lens replacement, use of lens case, and manufacturer's recommended replacement frequency as defined by the participants' selection of their habitual lenses using a photographic aide. Daily disposable wearers were identified as reporting daily replacement (by self-report and lens identification) and not using a lens case. If there was a discrepancy among these three factors, the lens assignment was assessed as a majority response (two of three) or as missing if conflicting information was reported.

The cohort was approximately two-thirds (68.7%) female and ranged from 12 to 33 years of age. A total of 154 participants (14.5%) were classified as daily disposable wearers and 896 (84.6%) as reusable wearers. Congruence was observed among all three daily disposable assignment factors for only 106 wearers (68.8%). The greatest discrepancy among daily disposable wearers was the report of using a lens case (n = 32 [20.8%]). In contrast, reusable lens wearers were more likely to report agreement across all three factors (n = 798 [89.1%], P < .001).

This analysis suggests that the report of not using a lens case is a more conservative surrogate for true single-use lens wear, as one in five may be storing and reusing their daily disposable lenses.