Purpose. To evaluate the effect of negatively powered soft contact lenses on ocular higher-order aberrations (HOAs).
Methods. HOA measurements were performed with fixed optical zones of 4.0 and 6.0 mm on 20 eyes of 10 participants before and minutes after wearing extended-wear Focus NIGHT & DAY contact lenses. For each eye, three contact lens powers were used: −2.00 diopters (D), –4.00 D, and a power equal to the spherical equivalent of each eye.
Results. The change in spherical aberration was highly correlated with the change in negative power of the contact lens at an optical zone of 4 and 6 mm (Pearson correlation coefficient = 0.914 and 0.743, respectively, P<0.0001). Total HOAs had a weaker but important correlation at an optical zone of 6 mm (Pearson correlation coefficient = 0.470, P=0.037) and insignificant correlation at an optical zone of 4 mm. Coma and trefoil were poorly correlated with contact lens power in either optical zone. Compared to the control using both optical zones, the –2.00 D contact lens resulted in a significant increase in total HOAs and spherical aberration, whereas the –6.00 D lens yielded a marked decrease in spherical aberration and a mild, statistically insignificant increase in total HOAs. Both contact lens powers yielded larger ocular coma and unchanged trefoil levels. The change from induction to reduction of spherical aberration occurred at –4.00 D.
Conclusions. The Focus NIGHT & DAY lens vehicle harbors positive spherical aberration and coma, independently of the lens power. The negative power of contact lenses induces negative spherical aberration, which, at large values, compensates for the lens vehicle positive spherical aberration to produce a net negative spherical aberration.