The Effects of Tween 20 onin vitroBovine Lenses

The optical properties of the cultured bovine lens were analyzed after exposure to various concentrations of Tween 20, a nonionic surfactant, to find a nonirritating concentration for commercial products. Bovine lenses were extracted and placed into a culture chamber for 24 hours at 37 degrees C with 4 - 5% CO2. The lenses were placed into three treatment (1%, n = 10; 10%, n = 9; and 100%, n = 10 Tween 20) and one control group (n = 7) for 15 minutes. For 8 days following treatment, the lens optics were analyzed periodically for back vertex distance ( focal length) and back vertex distance variability ( sharpness of focus) using a laser-scanning device. For both the control and the 1% Tween 20 condition, no significant change was seen from the beginning of the experiment ( p > 0.05). The 10% Tween 20 solution induced significant loss of sharp focus (0.62 +/- 0.1mm SEM) 4 hours after exposure, increasing to BVD 1.69 +/- 0.3 mm SEM by the end of experimentation ( p < 0.05). At full strength ( 100%), Tween 20 began to cause damage after 4 hours (BVD = 0.50 +/- 0.06 mm SEM), and this change increased to BVD = 4.46 +/- 0.59 mm SEM after 8 days following treatment ( p < 0.05). Therefore, a dose-dependant increase in back vertex distance ( BVD) variability was detected. This research suggests that using 1% Tween 20 in commercial solutions should not produce ocular irritation, whereas concentrations above 10% will cause significant irritation. As well, the bovine lens assay, paired with the automated lens scanner, provided a sensitive approach to measure mild ocular irritation.