Parameter consistency in disposable lenses

An evaluation of parameter consistency and edge defects as they might relate to premature lens fracture was undertaken for 2 disposable lens types, 50 Johnson & Johnson Acuvue lenses and 50 Wesley-Jessen FreshLook lenses. Diameter measurements varied from 13.97 to 14.48 mm (mean = 14.28 mm, SD = 0.138 mm) for Acuvue and 14.30 to 14.63 mm (mean = 14.41 mm, SD = 0.064 mm) for FreshLook. Based on previously reported information, these diameter variations for Acuvue may be sufficient to affect lens fitting characteristics. Calculated back surface sagittal depth varied from 3.27 to 3.38 mm (mean = 3.32, SD = 0.029 mm) for Acuvue and 3.68 to 3.87 mm (mean = 3.75 mm, SD = 0.039 mm) for FreshLook. Center thickness was generally consistent across the power range evaluated (-0.50 to -4.00 D) for the FreshLook lenses, and appeared to increase significantly for low minus powers for the Acuvue lenses. Twenty-one (44%) Acuvue lenses and 6 (12%) FreshLook lenses showed edge defects that might contribute to premature lens fracture.