Corneal epithelial disruption with extremely thin hydrogel lenses

Recent reports indicate that acute and chronic adverse effects of extended wear contact lenses may be overcome with lenses of higher oxygen transmissibility. For hydrogel lenses, higher water content and thinner lenses have been proposed. Several studies have shown corneal epithelial disturbance with thin high water hydrogel lenses. In this study hydrogel lenses of 38, 55, 65 and 75% water were tested in a -3.00 D monocurve lens design and in a parallel lens design. Center thicknesses were the thinnest yet reported, ranging from 0.022 to 0.036 mm. Subjects stayed in a low humidity (25–35%) environment for a 6 hour testing period. With regard to epithelial disturbance, the results show a trend that the higher the water content the earlier the onset, the greater the maximum level and the greater percentage subjects that exhibited the epithelial disruption. The -3.00 D lenses produced more epithelial disturbance than the parallel designs. The location of the disturbed epithelium was central for the - 3.00 D lenses and along the lid margins for the parallel lenses. Between onset and termination of the study at six hours, the severity of epithelial disturbance waxed and waned. These results do not concur with the current understanding of the mechanism of epithelial disturbance with thin high water hydrogel lenses and suggest the need for further evaluations.