Purpose: The aim of this study is to investigate the effect of contact lenses on the optical performance of the eye by measuring wavefront aberrations for the eyes with or without contact lenses. Method: A sensitive aberrometer was used to measure wavefront aberrations for 54 eyes in 27 subjects at three contact lenses wearing conditions: with no contact lens (non-CL), with soft-contact lenses (soft-CL) and with RGP contact lenses (RGP-CL). Root-Mean-Square (RMS) of the wavefront aberrations and Zernike aberrations were calculated. Results: Change in RMS values of wavefront aberrations with CL wearing was observed for every eye with substantial individual variation. Relative to the mean RMS value for non-CL condition, the mean RMS value was increased for soft-CL condition and was significantly reduced for RGP-CL condition. Significant increase in mean RMS for soft-CL condition was found when astigmatisms were removed. While the soft-CL wearing was result in significant increases in higher orders of Zernike aberrations (4th, 5th and higher), the RGP-CL led significant decrease in 2nd order of Zernike aberrations. For the eyes with low wavefront aberrations in the non-CL condition, either soft-CL wearing or RGP-CL wearing has shown increases in RMS values. Conclusion: Contact lenses wearing, either the soft-CL or the RGP-CL, causes change in wavefront aberrations of the eye. The changes in wavefront aberrations vary substantially from eye to eye. While the soft-CL wearing tends to induce more higher order aberrations, the RGP-CL effectively reduces the astigmatisms. Both the soft-CL and RGP-CL induce more aberrations for the eyes that have low wavefront aberrations. The change in wavefront aberrations due to the contact lenses wearing may explain the change in visual performances for contact lenses wearers reported previously.