Structural and optical changes in the eye after soft contact lens wear

Purpose To investigate the magnitude and aetiology of structural and optical changes in the cornea after short-term hydrogel contact lens wear and to explore the effect of these changes on visual performance. Methods Sixteen healthy subjects were fitted with a low-Dk hydrogel contact lens (CH) in one eye and a silicone hydrogel (SH) lens in the contralateral eye. Subjects wore the lenses for 1 month in daily wear (DW) and 1 week in extended wear (EW), with at least 1 week ‘wash out’ in between. All lenses were plano powered and were manufactured in matched designs with the same specifications. Measurements of corneal topography, corneal pachymetry (apical and peripheral), and corneal and ocular aberrations were performed at baseline and after lens wear using a Scheimpflug imaging system (Oculus Pentacam) and a Hartmann-Shack aberrometer (IRX3). Best corrected visual acuity (BCVA, logMAR) and contrast sensitivity measurements (CS, Pelli-Robson) were also performed. Results The optical and structural changes in the cornea after 1 month of DW and 1 week of EW for both the CH and SH materials were of low magnitude. The topographic and pachymetric changes observed were not found to be significant (p>0.05, repeated measures ANOVA). After 1 month of DW, however, the corneal root mean square of quatrefoil aberrations was found to be significantly different after CH contact lens wear (mean difference -0.021 µm; 95% confidence interval for difference: -0.037 to -0.06 µm; p=0.003). BCVA and CS did not change significantly after lens wear. Conclusion Our data showed that the CH and SH lenses tested do not significantly alter the structure or the optical performance of the cornea after one month of daily wear and 1 week of extended contact lens wear.