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M. L. Read, C. Maldonado-Codina, P. B. Morgan; Investigating the Influence of Manufacturing Batch on the Repeatability of Dynamic Contact Angle Measurements for Hydrogel Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1521.
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© ARVO (1962-2015); The Authors (2016-present)
This study aims to investigate the influence of manufacturing batch on the repeatability of dynamic contact angle measurements for hydrogel contact lenses.
Three silicone hydrogel contact lenses (senofilcon A, balafilcon A and lotrafilcon A) and one hydrogel contact lens (etafilcon A) were investigated. Contact angles were measured with an OCA-20 contact angle analyser (Dataphysics Instruments, Germany) using a dynamic captive bubble technique. Ten lenses were evaluated per brand (five lenses from the same manufacturing batch (intra-batch) and five lenses from different manufacturing batches (inter-batch)). Each lens was measured five times. All investigations were fully masked and randomised. Coefficient of repeatability (COR) values and 95% confidence intervals were calculated. Differences between COR values were deemed to be statistically significant when there was no overlap between the relevant 95% confidence intervals.
Advancing contact angle COR values ranged between 3.5° (senofilcon A) and 6.8° (etafilcon A) for intra-batch lenses, and between 3.4° (senofilcon A) and 20.0° (lotrafilcon A) for inter-batch lenses. Receding contact angle COR values ranged between 3.7° (lotrafilcon A) and 5.7° (etafilcon A) for intra-batch lenses, and between 2.3° (lotrafilcon A) and 5.7° (etafilcon A) for inter-batch lenses. For the receding contact angle COR values for all study lenses showed overlap of the 95% confidence intervals. For the advancing contact angle COR values, overlap of the 95% confidence intervals was present for etafilcon A and senofilcon A, but not for lotrafilcon A or balafilcon A.
All contact lenses investigated showed similar receding contact angle repeatability between lenses from the same and from different manufacturing batches. However, advancing contact angles showed less good repeatability for lenses from different manufacturing batches compared to those from the same manufacturing batch for lotrafilcon A and balafilcon A. Both these lenses undergo a plasma surface treatment during manufacture, perhaps suggesting that lenses which undergo post-polymerisation surface treatment may display a greater degree of in vitro surface wetting variability between manufacturing batches than lenses manufactured without such a treatment. This work also highlights the importance of selecting lenses from a number of batches when measuring contact lens material characteristics.
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