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 pigment-free optical zone diameter decreased. Therefore, consumers of tinted lenses should be informed about the possible disturbance in visual function.

Trial registration number

NCT02537275.