Effect of 30-day continuous wear of silicone hydrogel contact lenses on corneal thickness

To investigate the effect of 30-day continuous-wear contact lenses (Focus Night & Day) on corneal thickness and physiology.

Twenty-six myopic eyes with no history of contact lens wear were fitted with silicone hydrogel contact lenses. Complete ophthalmologic examinations, corneal topography, and corneal thickness measurements at the center and eight peripheral areas were performed before fitting and at each visit, namely on day 1, day 10, and 1 month. Mean corneal thicknesses were statistically compared by using one-way repeated-measures analysis of variance.

All patients maintained their 20/20 vision with correction. Limbal vascularization was noted in one patient at the end of the study. No patient had subjective complaints. In another patient, a punctate corneal epithelial defect was noted on the 15th day, but it healed when the contact lens was removed for a day. The mean corneal thicknesses in different regions were significantly increased by approximately 14 to 38 microm compared with baseline measurements. There were no significant differences between the corneal topography taken on the first day and the one taken at the end of the first month.

All patients maintained their visual acuity. Apart from the limbal vascularization and punctate epithelial corneal defects, which resolved when the contact lens was removed for 1 day, no serious complications were noted. Despite the high oxygen permeability of the monthly Night & Day contact lenses, the mean central and peripheral corneal thicknesses increased. These increases indicate that these lenses may have an effect on corneal metabolism.