Peter Hagmann

Measured versus labeled parameters of daily disposable contact lenses

Abstract The daily disposable wearing modality places extremely high demands on manufacturers to ensure consistent lens quality. The high replacement rate and short usage interval may sensitize wearers to day-to-day variations in lens power and geometrical parameters. This study compared three daily disposable lenses for conformity with their labeled parameters of center thickness, diameter, base curve equivalent, and sphere power and evaluated the variability in each of these parameters. Thirty daily disposable lenses of labeled sphere powers −1.00, −3.00, and −6.00 D made from nelfilcon A, etafilcon A, and filcon 3A ∗ ∗At the time of publication no USAN name had been issued for this material. The British ACLM classification has therefore been used. were randomized, masked, and measured in triplicate. Descriptive statistics of mean, standard deviation, and range from maximum to minimum were compared with the labeled parameters. Inferential statistical comparisons using the general linear model with the significance level of 0.05 for differences from labeled parameters were performed. Nelfilcon A lenses more closely approximated their labeled parameters for center thickness, diameter, base curve, and sphere power than either etafilcon A or filcon 3A lenses. Standard deviations and ranges for differences from labeled parameters for nelfilcon A were predominantly lower than for the comparative materials. Filcon 3A lenses tended to be less consistent with their labeled parameters than the other materials. Although the difference for an individual parameter from its labeled specification might not result in clinically significant performance effects, the cumulative effect of higher standard deviation or range of differences for several parameters may result in lenses that vary in performance or fitting from lens to lens. In the absence of in-office inspection and verification of each lens that a patient wears, a more predictable lens should assist eye care professionals with patient management.