Effect of the pigment-free optical zone diameter of decorative tinted soft contact lenses on visual function

Aims: We investigated changes in visual function after wearing decorative tinted soft contact lenses with different pigment-free optical zone diameters. Methods: A prospective study was performed in 30 eyes of 30 healthy volunteers. Best-corrected visual acuity (BCVA), ocular higher-order aberrations (HOAs), modulation transfer function (MTF), Strehl ratio and contrast sensitivity were evaluated after wearing clear lens and tinted lenses with different pigment-free optical zone diameters (4, 5 and 6 mm). Results: BCVA decreased from 0.00 logMAR after wearing a clear lens to 0.04±0.04 logMAR after wearing 4 mm optical zone lens (p<0.001). As the optical zone diameter decreased, ocular aberrations were induced. Total HOAs, coma aberration and secondary astigmatism showed significant difference between clear lens and 5 or 4 mm optical zone lenses (p<0.050). Spherical aberration and trefoil showed significant difference between clear lens and 4 mm optical zone lens (p<0.050). The results for Strehl ratio revealed poorer optical quality for both 5 and 4 mm optical zone lens (both p=0.002). The entire ocular MTF was significantly different, corresponding to the decreased optical zone diameter. The HOAs showed a correlation with the blocked pupil covered by the tinted part (r=0.435, p<0.001). In photopic and mesopic conditions, the contrast sensitivity decreased significantly with the reduced pigment-free optical zone diameters. Conclusion: Decorative tinted contact lenses significantly increased ocular aberrations and decreased optical quality and contrast sensitivity, as the pigmentfree optical zone diameter decreased. Therefore, consumers of tinted lenses should be informed about the possible disturbance in visual function.