Abstract
Purpose::
Changes in wavefront aberration for myopic eyes wearing different contact lenses were revealed in a previous study (Lu, et al. OVS 2003). The consequent effect of the aberration change on visual performance, however, is not well understood. The purpose of this study is to measure visual acuity under various contrasts when wearing different contact lenses.
Methods::
Wavefront aberrations and visual acuities at four contrast levels (100%, 25%, 10% and 5%) were tested using an aberrometer (WASCA, Carl Zeiss Meditec) and a VA tester (MFVA-100, Shenzhen BriteEye) respectively for 42 eyes of 22 young myopes with spherical error from -1.75D to -8.50D (mean = -4.97D) under three refractive error corrected conditions with: 1) spectacle lenses fully correcting refractive error (SP), 2) soft contact lenses (Surevue, J&J) correcting spherical error (Soft-CL), and 3) RGP contact lens (XO, Boston) correcting spherical error (RGP-LC).
Results::
Relative to SP wearing condition, RMS of wavefront aberrations was significantly increased for Soft-CL wear (t=2.210, p<0.05), but not significantly changed under RGP-CL condition. Mean visual acuity for the SP condition were -0.086, 0.068, 0.271, 0.449 logMAR at 100%, 25%, 10% and 5% contrast levels respectively. The visual acuity was significantly decreased by 0.011(100%), 0.034(25%), 0.064(10%) and 0.082(5%) logMAR for Soft-CL wear (F=5.56, p<0.001). Meanwhile, the visual acuity was significantly improved by -0.053 (100%), -0.042 (25%), -0.045 (10%) and 0.001 (5%) when RGP-CL was worn (F=3.897, p=0.001). The change in visual acuity at low contrast level (5%) was significantly correlated with an increase in RMS for the Soft-CL condition (r=0.411, p=0.007).
Conclusions::
The results suggest that different type of contact lenses have different effects on visual performance due to their specific influence on wavefront aberrations. While Soft-CL wear induces more aberrations and cause decreases in visual acuity, RGP-CL wear reduces aberrations and improves visual acuity.
Keywords: contact lens • visual acuity • optical properties